feat(integrations): support SPECIFY_<KEY>_EXTRA_ARGS env var for agent subprocess flags (#2596)

* feat(integrations): support SPECIFY_<KEY>_EXTRA_ARGS env var for agent subprocess flags

Read a per-integration env var (SPECIFY_<KEY>_EXTRA_ARGS) inside
`SkillsIntegration.build_exec_args`, `MarkdownIntegration.build_exec_args`,
and `TomlIntegration.build_exec_args` and append the parsed flags to the
spawned agent's argv, gated per integration key.

Operators can now opt into extra CLI flags (e.g.
`SPECIFY_CLAUDE_EXTRA_ARGS=--dangerously-skip-permissions`) without
modifying any SKILL or workflow YAML. Useful in CI / non-interactive
contexts where the spawned `<agent> -p ...` would otherwise hang on
an internal permission or input prompt invisible to the parent
`specify workflow run` process.

Key normalization: `kiro-cli` → `SPECIFY_KIRO_CLI_EXTRA_ARGS` (hyphen
replaced with underscore, then uppercased).

Default (env var unset or whitespace-only) is byte-identical to
previous behaviour. Extra args are inserted between `-p prompt` and
the model / output-format flags so they cannot clobber canonical
Spec Kit args.

Implementation: a single helper `IntegrationBase._apply_extra_args_env_var`
encapsulates the env-var read + shlex parsing; each of the three
concrete `build_exec_args` implementations calls it.

Closes #2595

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(integrations): wire SPECIFY_<KEY>_EXTRA_ARGS into Codex/Devin/Opencode/Copilot

Four integrations override `build_exec_args` and were silently
ignoring the env-var hook introduced in the previous commit:

- CodexIntegration (`codex exec ...`)
- DevinIntegration (`devin -p ...`)
- OpencodeIntegration (`opencode run ...`)
- CopilotIntegration (`copilot -p ...`)

Each now calls `self._apply_extra_args_env_var(args)` between the
base argv and the canonical Spec Kit flags (matching the placement
in `MarkdownIntegration`, `TomlIntegration`, and `SkillsIntegration`),
so operator-injected flags cannot clobber `--model` / `--output-format`
/ `--json`.

Adds 4 parameterized override-integration tests locking the wiring
per agent. Also cleans up an inline `__import__("os").environ` in the
fixture to a top-of-file `import os`.

Drive-by typing fix: guard `self.registrar_config.get(...)` in
`CopilotIntegration.add_commands` against the `None` case, matching
the pattern already used in `base.py` for the same access.

Addresses Copilot review on #2596.

* fix(integrations): apply Opencode extra-args before prompt-derived --command

When the Opencode prompt starts with `/`, `build_exec_args` injects
`--command <X>` derived from the prompt. The previous placement of
`self._apply_extra_args_env_var(args)` appended operator-injected
args AFTER that `--command`, so a user setting
`SPECIFY_OPENCODE_EXTRA_ARGS="--command override"` could redirect the
command under typical last-wins repeated-flag CLI semantics.

Move the hook to immediately after `args = [self.key, "run"]`, before
the prompt-parsing block. The operator's `--command override` (if
any) now precedes the Spec Kit-derived `--command speckit`, so the
canonical choice wins.

Adds `test_opencode_extra_args_cannot_clobber_prompt_derived_command`
locking the ordering. Also corrects the module docstring to describe
the hook as living in `IntegrationBase` (not `SkillsIntegration`) and
to acknowledge that this file covers Codex/Devin/Opencode/Copilot in
addition to SkillsIntegration stubs.

Addresses Copilot review on #2596.

* fix(integrations): honour SPECIFY_COPILOT_EXTRA_ARGS in dispatch_command

`CopilotIntegration` is the only integration that overrides
`dispatch_command` — it builds `cli_args` inline rather than going
through `build_exec_args`. The previous commit wired
`_apply_extra_args_env_var` into `build_exec_args` but workflow
execution calls `dispatch_command`, so `SPECIFY_COPILOT_EXTRA_ARGS`
was silently ignored at runtime.

Add the hook in `dispatch_command` immediately after
`cli_args = ["copilot", "-p", prompt]`, mirroring the placement in
`build_exec_args` (between `-p prompt` and the canonical
`--agent` / `--yolo` / `--model` / `--output-format` flags).

`IntegrationBase.dispatch_command` already delegates to
`build_exec_args`, so Codex, Devin, and Opencode continue to honour
their respective env vars through inheritance — no further changes
needed for them.

Adds two end-to-end tests that monkeypatch `subprocess.run` and
assert the env-var args reach the executed argv:
- `test_copilot_dispatch_command_includes_extra_args` locks the
  bypass fix on the overridden path.
- `test_codex_dispatch_command_includes_extra_args` locks the
  inherited-base-dispatch path for the other three integrations.

Addresses Copilot review on #2596.

* refactor(integrations): rename env var to SPECIFY_INTEGRATION_<KEY>_EXTRA_ARGS

Per maintainer request: scope the operator-injected env var to the
integration subsystem by prepending `INTEGRATION_` to the key
segment, so it does not collide with other Spec Kit env-var
namespaces.

Renames everywhere it appears:
- Helper `IntegrationBase._apply_extra_args_env_var` env_name
  format and docstring (`base.py`).
- Inline comment in `CopilotIntegration.dispatch_command`.
- All `monkeypatch.setenv(...)` calls, docstrings, and the
  autouse fixture's scope filter in
  `tests/integrations/test_extra_args.py`.

No behaviour change beyond the variable name. Default (env var
unset) still byte-identical to before this PR.

Addresses review on #2596.

* fix(integrations): raise actionable error on malformed EXTRA_ARGS quoting

Wrap `shlex.split` in `_apply_extra_args_env_var` so an unmatched quote
in `SPECIFY_INTEGRATION_<KEY>_EXTRA_ARGS` surfaces a clear `ValueError`
naming the offending env var and showing the invalid value, instead of
crashing workflow dispatch with a bare shlex traceback. Adds a new test
locking the actionable error path.

Addresses Copilot review feedback on #2596.

* test(integrations): use `_copilot_executable()` in Copilot extra-args test

`test_copilot_integration_honours_extra_args` hardcoded `"copilot"`
in the expected argv, but `CopilotIntegration.build_exec_args` calls
`_copilot_executable()` which returns `"copilot.cmd"` on Windows
(`os.name == "nt"`). The test passed on Linux/macOS and failed on
all three Windows-latest matrix entries.

Resolve by importing `_copilot_executable` alongside `CopilotIntegration`
and using it as the first expected argv token. The companion
`test_copilot_dispatch_command_includes_extra_args` already uses
`index()` lookups rather than full-argv equality so it was unaffected.

* fix(integrations): couple Codex executable to self.key + cover base classes

Two Copilot findings on the latest pass:

1. `CodexIntegration.build_exec_args` hardcoded the executable name
   as the literal `"codex"` while the env-var lookup derives from
   `self.key`. The two should stay coupled (matching Devin/Opencode,
   which both use `self.key` already). Replace the literal with
   `self.key` so the argv and env-var scoping cannot drift.

2. `tests/integrations/test_extra_args.py` covered the
   `SkillsIntegration` mechanism (via stubs near the top) and the
   four `build_exec_args` overrides (Codex/Devin/Opencode/Copilot)
   end-to-end, but did not exercise the `MarkdownIntegration` or
   `TomlIntegration` base implementations directly. Add bare
   `_MarkdownAgentStub` and `_TomlAgentStub` test stubs and a test
   each — the most common integration pattern (Amp, Auggie, Generic,
   Gemini, Tabnine, …) inherits without overriding, so the base
   wiring is now locked.

Full suite: 3011 passed (was 3009), 40 skipped, no regressions.

Addresses Copilot review feedback on #2596.

* fix(integrations): rename env var to SPECKIT_INTEGRATION_<KEY>_EXTRA_ARGS

Renames the env-var hook prefix from `SPECIFY_INTEGRATION_*` to
`SPECKIT_INTEGRATION_*` to match the established codebase
convention for integration-subsystem env vars
(`SPECKIT_INTEGRATION_CATALOG_URL` in `integrations/catalog.py`,
`SPECKIT_COPILOT_ALLOW_ALL_TOOLS` in `integrations/copilot/__init__.py`).

The `SPECIFY_*` prefix is reserved for user-facing
feature-resolution variables (`SPECIFY_FEATURE`,
`SPECIFY_FEATURE_DIRECTORY`); reusing it for integration-subsystem
scoping would introduce a second integration namespace under a
different prefix, confusing operators who already set
`SPECKIT_INTEGRATION_CATALOG_URL`.

Also reverts the unrelated defensive `arg_placeholder` /
`registrar_config is None` guard in
`CopilotIntegration.setup_skills_mode` — it was a drive-by pyright
cleanup mixed into this PR. Every concrete integration sets
`registrar_config` so the guard never fires in practice; the
typing issue belongs in a focused follow-up rather than this
env-var-hook PR.

Updates everywhere the old prefix appeared:
- `IntegrationBase._apply_extra_args_env_var` helper + docstring
- `CopilotIntegration.dispatch_command` inline comment
- All `monkeypatch.setenv(...)` calls in `tests/integrations/test_extra_args.py`
- The autouse fixture scope filter
- Test module docstring

Full suite: 3011 passed, 40 skipped, no regressions.

Addresses Copilot review feedback on #2596.

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>