feat(plane): honest coverage in alerts; PHP alerts from the engine on the host

Quick mode has rules only for c/cpp, groovy, java, javascript/typescript and
python, so every PHP case's "0 alerts" read as clean. The `alerts` task now
records per language of the files read whether quick mode covers it
(derived from the bundled ruleset, not a list): coverage quick | none, with
file counts per pin, and `uncovered`. `remember` turns that into `coverage`
memory rows (a new kind; the Run passes the alerts summary.json as input),
loop-measure reports coverage per language, and improve/memory.py's M1/M2
skip a repository+pin whose coverage for the rule's language is only
`none` (counted under `coverage_none` in the proposal's excluded).

`ousast plane alerts-engine <Run.yaml> --source <frozen export>`
(plane/engine_alerts.py) does the alerts task on the host for cases whose
files include a language the engine covers but quick mode does not (PHP):
exports both pins from the case cache, runs the quick scan and the
openultrasast:dev engine container (finding_dump.py, --network none,
--memory 3g, one at a time, per-pin deadline), writes engine findings in
the alerts.jsonl row shape (rule_id engine:<family>, source engine,
in_fix_range from case.json) with a summary (files read, questions,
completed, seconds, degradations per pin), and marks the task done via
reconciler.mark_done. No result, no files read, or questions == 0 fails
loudly and leaves the run untouched. Refuses a git checkout as source.

Runner image rebuilt and re-pinned (sha256:ebb40a9a...); validation-46
regenerated (digest only). Live, recorded in
benchmarks/measurements/2026-09-30-php-engine-alerts/: froxlor 366 files,
130/130 questions per pin, 6 alerts per pin, 0 in the fix range; wp-gopay
19 files, 101/101 questions, 0 alerts. The loop: 32 run rows (coverage 8,
php=engine), 0 proposals, gate no_proposals, $0.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01EmM1j46qgKMh3zqD1QMwEo

src/openultrasast/plane/memory.py

@@ -1,7 +1,7 @@
 """The plane's memory store (harnessx-removal Requirement 6.1/6.4, design section 4).
 
 One store, keyed by repository and pin, holds what plane runs learned: repository facts by content hash, and rows
-of five kinds (``facts``, ``verdict``, ``unit_cost``, ``alert``, ``proposal_outcome``) that the ``remember`` task
+of six kinds (``facts``, ``verdict``, ``unit_cost``, ``alert``, ``coverage``, ``proposal_outcome``) that ``remember``
 (:mod:`.tasks.remember`) derives from a run's delivered artifacts. Layout, identical for both backends::
 
     index.jsonl                               one row per ingested (run, task): sha256 of its rows, row count
@@ -49,7 +49,7 @@ MEMORY_KEY_ANNOTATION = "openultrasast.io/memory-key"
 POPULATION_ANNOTATION = "openultrasast.io/population"
 SPLIT_ANNOTATION = "openultrasast.io/split"
 SNAPSHOT_ANNOTATION = "openultrasast.io/memory-snapshot"  # the loop's guard: {"catalog", "manifest", "populations"}
-KINDS = ("facts", "verdict", "unit_cost", "alert", "proposal_outcome")
+KINDS = ("facts", "verdict", "unit_cost", "alert", "coverage", "proposal_outcome")
 ROW_FIELDS = ("id", "kind", "repo", "pin", "run", "task", "population", "split", "image")
 TAG_FIELDS = ("repo", "pin", "kind", "family", "run", "population", "split")
 MIN_FREE_BYTES = 1 << 30