Clean up validate_fast.sh Phase 4 TODOs and remove project-specific references

[stranske]

Topic GUID: 06e94437-09a3-5519-af2f-ee625aada267

Why

scripts/validate_fast.sh contains 12 TODO Phase 4 markers referencing Trend_Model_Project-specific features (SRC_FILES detection, autofix tests, coverage requirements) that are not applicable to this workflow repository. These dead code paths and stale references cause confusion and add maintenance burden.
Scope

• scripts/validate_fast.sh cleanup of TODO markers and project-specific detection logic.

Tasks

• Remove all TODO Phase 4 markers and their associated dead/commented code blocks.
• Remove SRC_FILES and AUTOFIX_FILES detection logic that references src/ directory patterns not present in this repo.
• Update linting targets to use scripts/ and .github/ instead of src/ tests/.
• Replace Python package-specific validation (coverage requirements, import tests) with workflow-specific checks (actionlint, YAML validation).
• Ensure the script still runs successfully after cleanup.

Acceptance criteria

• grep -c "TODO Phase" scripts/validate_fast.sh returns 0.
• Script executes without errors: bash scripts/validate_fast.sh --help works.
• No references to src/ directory or Trend_Model_Project-specific patterns remain.
• Validation targets are appropriate for a workflow repository (scripts/, .github/).

Implementation notes

• Keep the core validation framework intact; only remove dead code and update targets.
• Test with bash scripts/validate_fast.sh --verbose to verify functionality after changes.
• Preserve the intelligent change detection but update the file patterns it looks for.

---

Synced by workflow run.

[github-actions]

Branch codex/issue-4 created from main.

Option 1 (Invite) is enforced on issue events. PR creation is disabled by design so you are the PR author. Codex only engages on human-authored PRs.

Please open the PR as the author so Codex can work on it:

• Compare link: https://github.com/stranske/Workflows/compare/main...codex/issue-4?expand=1
• Suggested title: Codex bootstrap for #4
• Suggested body (copy/paste):

### Keepalive: OFF
<!-- meta:issue:4 -->

### Source Issue #4: Clean up validate_fast.sh Phase 4 TODOs and remove project-specific references

Base: main
Head: codex/issue-4

Source: https://github.com/stranske/Workflows/issues/4

> Topic GUID: 06e94437-09a3-5519-af2f-ee625aada267
> 
> ## Why
> `scripts/validate_fast.sh` contains 12 TODO Phase 4 markers referencing Trend_Model_Project-specific features (SRC_FILES detection, autofix tests, coverage requirements) that are not applicable to this workflow repository. These dead code paths and stale references cause confusion and add maintenance burden.
> Scope
> - `scripts/validate_fast.sh` cleanup of TODO markers and project-specific detection logic.
> 
> ## Tasks
> - [ ] Remove all TODO Phase 4 markers and their associated dead/commented code blocks.
> - [ ] Remove SRC_FILES and AUTOFIX_FILES detection logic that references `src/` directory patterns not present in this repo.
> - [ ] Update linting targets to use `scripts/` and `.github/` instead of `src/ tests/`.
> - [ ] Replace Python package-specific validation (coverage requirements, import tests) with workflow-specific checks (actionlint, YAML validation).
> - [ ] Ensure the script still runs successfully after cleanup.
> 
> ## Acceptance criteria
> - `grep -c "TODO Phase" scripts/validate_fast.sh` returns 0.
> - Script executes without errors: `bash scripts/validate_fast.sh --help` works.
> - No references to `src/` directory or Trend_Model_Project-specific patterns remain.
> - Validation targets are appropriate for a workflow repository (scripts/, .github/).
> 
> ## Implementation notes
> - Keep the core validation framework intact; only remove dead code and update targets.
> - Test with `bash scripts/validate_fast.sh --verbose` to verify functionality after changes.
> - Preserve the intelligent change detection but update the file patterns it looks for.
> 
> ---
> Synced by [workflow run](https://github.com/stranske/Workflows/actions/runs/20290022575).

@codex start

Codex, please derive and propose:
- Scope / key constraints
- Acceptance criteria / definition of done
- Initial task checklist to iterate through

Use the issue details above to draft the plan, then proceed with implementation.

---

Once the plan is posted, comment the snippet below to start execution and enable keepalive:

The following block should be pasted as a separate PR comment:

```markdown
@codex Your objective is to satisfy the **Acceptance Criteria** by completing each **Task** within the defined **Scope**.

**This round you MUST:**
1. Implement actual code or test changes that advance at least one incomplete task toward acceptance.
2. Commit meaningful source code (.py, .yml, .js, etc.)—not just status/docs updates.
3. Mark a task checkbox complete ONLY after verifying the implementation works.
4. **POST A REPLY COMMENT** with completed checkboxes using the **EXACT TEXT** from the lists below.

**CRITICAL - Checkbox Format:**
When posting your reply, copy the **exact checkbox text** from the Tasks and Acceptance Criteria sections below. Do NOT paraphrase or summarize. The automation matches text exactly.

Example format for your reply:

Completed this round

Tasks

• Add an environment flag (e.g., TREND_PIPELINE_PROXY_SIMPLE) that, when set, skips GC scanning...
• Ensure default behaviour remains unchanged (GC scanning enabled) to preserve test friendliness.

Acceptance Criteria

• Setting the new env flag yields a direct-import proxy path; default continues to honour GC-scanned modules.

**DO NOT:**
- Commit only status files, markdown summaries, or documentation when tasks require code.
- Re-post checklists without making implementation progress.
- Close the round without source-code changes when acceptance criteria require them.
- Paraphrase or shorten checkbox text—copy it exactly for tracking to work.

Review the Scope/Tasks/Acceptance below, identify the next incomplete task that requires code, implement it, then **post a reply comment** with the completed items using their **exact original text**.