feat(hygiene): detect orphan config files by reachability (#155)

[Jammy2211]

Part 1 of PyAutoBrain#155 — the detector

/hygiene config could not see orphan config files. _hygiene_config.py iterated only library yamls and skipped any without a workspace counterpart, so a workspace file the libraries never shipped was structurally invisible — how a dead config/grids.yaml survived in 10 repos for ~a year (autolens_workspace#317).

What this adds

An orphan-file pass beside the existing key-mirror diff. A workspace config/**/*.yaml with no library counterpart at the same relative path is an orphan.

The signal is reachability, not filename similarity — a pure filename check is ~120 hits, nearly all legitimate, because whole subtrees are owned by something other than the libraries. Those owners are named in an explicit ORPHAN_OWNERS map and suppressed:

• build/* → PyAutoHands release tooling
• priors/* → JSONPriorConfig class-path resolution

Deliberately an in-checker map, not a per-repo .hygieneignore — 20 new files and a config surface that can itself go stale is the exact failure mode being fixed.

The library's own shipped set encodes the verdict: it ships non_linear/GridSearch.yaml (live) but not non_linear/{nest,mle,mcmc}.yaml (dead), so the pass keeps the first and surfaces the rest with no per-file rule. Only repos whose config/ mirrors the library tree (share ≥1 file) are scanned, self-scoping to workspace/test/assistant repos and excluding organ repos — no hardcoded list.

Acceptance (all verified)

Case	Expected	Result
real pre-#317 grids.yaml blob	flag	✅
non_linear/{nest,mle,mcmc}.yaml today	flag	✅
build/*	silent	✅
priors/*	silent	✅

A check that cannot re-find the bug that motivated it is not validated — the grids.yaml retrospective runs against the real blob at ce99ca12b^.

What it found

Running it surfaced 26 dead non_linear files across 9 repos and a third cluster the ticket did not name — visualize/include.yaml in 2 test repos (no library ships it, nothing reads conf.instance["visualize"]["include"], no Include2D class, user-facing workspaces already dropped it). Both are removed in the Part-2 PRs below.

Tests

tests/test_hygiene_conductor.py: a suppressed-vs-flagged orphan fixture (the owner map is the part most likely to rot) and a non-mirror-repo skip. 16 passed. Stdlib+PyYAML only; the PyYAML-absent sys.exit(1) fallback preserved; folded into the same count|summary prescan line.

Part 2 — cleanup PRs (the dead config this found)

autocti_assistant, autocti_workspace, autocti_workspace_test, autofit_workspace_developer, autofit_workspace_test, autogalaxy_workspace_test, autolens_assistant, autolens_workspace_test, euclid_strong_lens_modeling_pipeline — all on feature/hygiene-orphan-config-files.

Closes #155.