fix(#108): proxy workspace scaffold no longer mistaken for user project (v2.0.47)

nalayahfowlkest-ship-it / zhangzhang-bit: real Windows project at
E:\Desktop\新建文件夹, model "analyzes" a non-existent empty Node
template named workspace-devinxse instead. zhangzhang-bit dumped what
the model actually receives — cascade upstream injects a
<workspace_information>/<workspace_layout> snapshot of the proxy's
seeded scaffold dir, and the model trusts that over the env-facts cwd.

Two-prong fix:

1. src/client.js scaffold no longer looks like a project. package.json
   name is "proxy-workspace-stub", README leads with "Proxy workspace
   placeholder", description says "NOT the user project". src/index.js
   is removed entirely. Plus an isLegacyScaffold migration that
   rewrites old "my-project" scaffolds in place on first cascade init
   after upgrade (existsSync would otherwise short-circuit the rewrite).

2. src/handlers/tool-emulation.js Environment facts block now also
   includes a one-line precedence note pointing at workspace_information/
   workspace_layout snapshots as proxy infrastructure. Wording carefully
   neutral — the project's banned-phrase rule (feedback_tool_preamble_rules.md)
   forbids "ignore"/"for this request only" because Opus' injection
   guard trips on them. Note only appears when env actually carries a
   cwd (otherwise it has no anchor to point at). Applied uniformly to
   all four preamble tiers (full, schema-compact, skinny, compact).

Tests: 480 -> 490 (+10 / 0 fail), new test/workspace-stub-108.test.js
covering all 4 preamble tiers carrying the note, the no-env skip, the
banned-phrase regression guard, scaffold rebrand, migration wiring,
and a defensive check that old "my-project" / "Hello, world" / "Getting
Started" strings stay gone.