fix: honor template overrides for tasks-template (#2278) (#2292)

* fix: honor template overrides for tasks-template (#2278)

- Add scripts/bash/setup-tasks.sh mirroring setup-plan.sh pattern
- Add scripts/powershell/setup-tasks.ps1 mirroring setup-plan.ps1 pattern
- Update tasks.md frontmatter to use dedicated setup-tasks scripts
- Resolve tasks template via override stack and emit path as TASKS_TEMPLATE in JSON output
- Reference resolved TASKS_TEMPLATE path in generate step instead of hardcoded path

* fix: remove stray EOF tokens from setup-tasks scripts

* fix: improve error messages for unresolved tasks-template

* test: update file inventory tests to include setup-tasks scripts

* fix: use Console::Error.WriteLine instead of Write-Error in setup-tasks.ps1

* fix: write prerequisite error messages to stderr in setup-tasks.ps1

* fix: validate tasks template is a file and normalize path in setup-tasks.ps1

* fix: improve tasks-template error message to mention full override stack

* test: add setup-tasks.sh to TestCopilotSkillsMode file inventory

* fix: skip feature-branch validation when feature.json pins FEATURE_DIR

* fix: correct override path in tasks-template error messages

* test: add integration tests for setup-tasks template resolution and branch validation

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* fix: correct fixture paths and add spec.md prerequisite checks

* fix: use correct .registry schema in preset priority test

* fix: remove stale aaa-preset block and duplicate comment in preset priority test

* fix: align preset directory names with registry IDs in priority test

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Co-authored-by: Nimraakram22 <nimra.akram123451@gmail.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>