CI: derive arch/source mapping from PlatformIO instead of hardcoding

[ayysasha]

Builds on #11151. Three of the hardcoded constants in generate_ci_matrix.py can be derived from PlatformIO, which makes the change-detection self-maintaining when a board/arch is added:

• Derive platform/<subdir> -> arch from build_src_filter. Each env re-includes its tree via +<platform/X>, so the reverse-map (including the ESP32 family self-grouping) is read from config. Drops ESP32_FAMILY and PLATFORM_SRC_TOPDIRS entirely, and fixes src/platform/extra_variants/ which was unmapped and fell back to a full build.
• Read [platformio] extra_configs for the env-definition ini globs instead of a hardcoded 2-glob tuple. Anti-rot / future-proofing; no behavior change on the current tree.
• _emittable is now an allowlist (None/pr/extra) so a retired or typo'd board_level fails closed rather than silently building. (Relevant now that community is being retired in this PR.)
• Workflow: drop the EXTRA / [[ -s ]] bash plumbing -- the generator no-ops on an absent/empty --changed-files, so it is passed unconditionally.

Verified against real PlatformIO: full, PR, and check sets plus every changed-file scenario produce identical matrices to this PR's head (zero under-build). 28/28 unit tests pass.

Targeted at feature/surgical-ci so a merge folds straight into #11151. Happy to reshape or split however you prefer.

Summary by CodeRabbit

• Bug Fixes

  • Improved pull-request CI matrix narrowing for both build and check jobs using the changed-files list when in PR context.
  • Updated change detection to derive platform/architecture relationships from PlatformIO metadata for more accurate target coverage.
  • Added stricter filtering so unknown or retired target levels are excluded (fails closed).

• Tests

  • Expanded CI matrix generation and selection tests to validate derived platform mappings, ini/glob discovery, base-inclusion behavior, and the tightened filtering rules.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 9867630 and a0600bc.

📒 Files selected for processing (2)

• bin/generate_ci_matrix.py
• bin/test_generate_ci_matrix.py

🚧 Files skipped from review as they are similar to previous changes (1)

• bin/generate_ci_matrix.py

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📝 Walkthrough

Walkthrough

The CI matrix generator now derives source-platform and family-base mappings from PlatformIO metadata, applies them during changed-file selection, and uses an allowlist for emitted levels. The PR workflow always passes the changed-files path, with expanded unit tests covering the derived behavior.

Changes

CI matrix narrowing

Layer / File(s)	Summary
PlatformIO metadata derivation bin/generate_ci_matrix.py	Normalizes extra_configs, scans environment definitions, extracts build_src_filter platform inclusions, and derives source-platform and family-base mappings.
Changed-file selection bin/generate_ci_matrix.py	Uses derived mappings for source-tree and architecture-ini matching, applies allowlisted emission levels, and preserves full-set fallback behavior.
PR workflow and validation .github/workflows/main_matrix.yml, bin/test_generate_ci_matrix.py	Always passes --changed-files in PR builds and tests source fan-out, metadata derivation, filtering, glob normalization, and base-ini classification.

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant GitHub Actions
  participant generate_ci_matrix.py
  participant PlatformIO metadata
  participant CI matrix
  GitHub Actions->>generate_ci_matrix.py: pass changed-files path
  generate_ci_matrix.py->>PlatformIO metadata: load environments and includes
  PlatformIO metadata-->>generate_ci_matrix.py: provide source and base-ini mappings
  generate_ci_matrix.py->>CI matrix: select and emit narrowed environments

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Suggested labels: github_actions

Suggested reviewers: vidplace7

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description is substantive, but it does not follow the required template and omits the attestations section.	Replace the freeform summary with the repository template and complete the testing/attestation checkboxes, including any affected hardware notes.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly states the main change: deriving CI arch/source mapping from PlatformIO instead of hardcoding.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@bin/generate_ci_matrix.py`:
- Around line 131-152: Update base_ini_platform_incl and select_changed so an
arch-base .ini with multiple direct platform includes is represented as an
ambiguous mapping and causes Tier-3 full fallback (None), rather than being
omitted and scoped to one top-level directory. Preserve the existing
single-include family mapping and no-include scoped behavior.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

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Run ID: fa3eeead-d5a2-4df9-9159-4781ad0f29bd

📥 Commits

Reviewing files that changed from the base of the PR and between 1e7bb3f and 9867630.

📒 Files selected for processing (3)

• .github/workflows/main_matrix.yml
• bin/generate_ci_matrix.py
• bin/test_generate_ci_matrix.py