fix(#595): doc-checkpoint asks whether the registry moved, not whether a file did

[localai-bot]

FEATURE_SURFACE_PREFIXES covered all of src/vllm/model_executor/models/, so
any edit to any model translation unit classified as feature_surface and owed
docs/FEATURES.md. That is the classify-by-directory trigger this file's own
header says the 2026-08-11 rewrite removed, still standing for model files:

A one-line compile fix owed three public-doc edits, so this gate produced 16
of the last 20 red CI runs, and it had accreted SIX hardcoded exact-path-set
escape hatches -- one per legitimate change it had blocked.
[...] Editing src/ alone owes nothing.

The cost stopped being hypothetical on 2026-08-16. e34d71379 (#1054) is a
one-line lambda-capture change to models/qwen3_5_weights.cpp that alters no
capability. The gate demanded the surface; the commit answered with prose in
BENCHMARKS, FEATURES and STATUS; that prose crossed the
check-public-doc-tables paragraph budgets; and because that checker also runs
in the pre-push hook, every branch in the repository was blocked from pushing.
That is #1055, re-filed by a second agent as #1062 with #1064 as a duplicate fix
PR, alongside #1058 which is still open. Two shared-file gates in series, each
individually defensible.

What the project supports is what the registry registers, so feature_surface
now keys off a change to the set of REGISTER_VLLM_MODEL(...) entries in the
touched file, read through blob() like the existing measurement_changes.
scripts/check-supported-models.py already gates docs/FEATURES.md against
that same set, so the signal is authoritative rather than newly invented.

This NARROWS a gate, which is the risky direction, so the polarity is pinned by
test rather than asserted: adding an architecture, adding a whole new registered
file, and removing an architecture each still owe docs/FEATURES.md, and the
four .agents/*-matrix.md records keep their path trigger because editing one
IS the claim.

Red before, green after, and mutation-proven. test_doc_checkpoint.py goes 27
-> 32 cases. Before the implementation, test_editing_a_registered_model_owes_nothing
failed with the FEATURES demand. After it, 32 pass. Because the three
still-owes cases were green under the OLD path trigger too, they could not by
themselves show the new trigger works, so registration_changes was mutated to
return []: that fails exactly those three and no others, and restoring returns
32 green.

Does not close #595. A genuine new architecture still writes the shared
docs/FEATURES.md table, so the lock that issue names survives; this removes
the contention for every fix, refactor and port phase that changes no
registration. #515 is the identical shape for CMakeLists.txt -> docs/USAGE.md
and is untouched. Both are recorded under ## Owed in the spec, together with
the class this narrowing gives up: a capability change inside an
already-registered model now goes undemanded.

Refs #595

FOLLOWING_AGENTS_PROTOCOL

Following-Agents-Protocol: true
AI-Assisted: true
Assisted-by: ClaudeCode:claude-opus-5 [ClaudeCode]