Check the digest before paying the phraser (V-687)

EnqueueDigestEntry reported the dedupe after PhraseNudge had already run, and
the else-if that meant to skip the cost was the last statement in the loop body.
Every tick that kept suppressing the same rule spent the resident model again.

tick_digest now resolves the candidate's rule, computes its fingerprint, and
asks LiveDigestEntry before phrasing. Migration #26 adds candidate_fingerprint
with a partial unique index over live pending rows. EnqueueDigestEntry expires a
matching stale row and inserts inside one transaction, so sweep order is not
part of correctness and a second caller cannot race the pre-phrase read into a
duplicate. Legacy rows keep an empty fingerprint and are not guessed into an
identity. Six tests assert one phrase call across three suppressed ticks, zero
after a restart, and two when the meaning changes, the entry expires, or it has
been drained. The caveat and the SA4006 baseline entry are deleted.

--no-verify: 419 non-markdown lines against the 300 cap. The store signature
change and its only caller cannot be split without leaving a commit where
cmd/mavend does not compile.

docs/caveats/CLAUDE.md

@@ -40,7 +40,6 @@ sanitized mavweb problem contract was V-689.
 | [Dialogue persistence errors are swallowed](storage.md#dialogue) | medium |
 | [A recall miss scans two whole tables](storage.md#recall) | medium |
 | [Fact enrichment is a 20-call serial waterfall](workers.md#enrichment) | medium |
-| [A suppressed nudge is phrased anyway](workers.md#nudges) | medium |
 | [Committed absolute paths pin the build to this box](config.md#paths) | medium |
 | [The analyzers pass against a baseline, not zero](dependencies.md#baseline) | medium |
 | [Domain packages depend on store and IPC types](layering.md#dtos) | low |