fix(shapes): the semantic arm proposes at the write-path floor, not a private 0.8 (#4208)

0.8 was sized for proposals nobody reads; every semantic proposal is read
by a judge before it is confirmed. Measured, it proposed 0 of 150 while
judged instances of a canon score 0.68-0.71 - the write-path hint's own
floor asks the same question of the same documents at 0.68. The arm now
uses that floor, scans 8 hits instead of 3 (a true instance ranked 4th
behind snippets of other language families), and the proposer version
bumps to 5 so rows examined under the old floor are read again.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

tests/test_integration_shape_classify.py

@@ -897,7 +897,7 @@ async def test_a_semantic_miss_does_not_silence_the_prompt(seeded):
     `confirmDanger` beside an async confirm canon is structurally identical to
     a registry helper beside an async service canon, and the arm's miss was
     meant to tell them apart. Measured live, true instances of a canon rarely
-    clear the arm's 0.8 floor either, so a miss fires on both — silencing on
+    clear the arm's floor either, so a miss fires on both — silencing on
     it silenced #2793's own case. Here the arm has read the body, found
     nothing, and the prompt is still RAISED.