fix(settings): quote numeric-shaped YAML keys so hash-keyed settings survive reload

The emitter wrote block-map keys raw while only values went through
quoting. A workspace-hash key segment that happens to be all digits
with a leading zero (or digits-e-digits) reloaded as an int/float —
leading zero dropped, or collapsed to Infinity — orphaning the stored
value. Hit ~1 in 1200 repos, deterministically and permanently: the
PATH preset (D-106) and the pre-existing Claude account binding for
such a repo vanished on every restart with no diagnostics. Same defect
class as the T-376 value-corruption fixes in this file; found by the
T-511 review pass, confirmed against the live store.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -44,6 +44,10 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 
 ### Fixed
 
+- Hash-keyed settings (per-workspace PATH presets, Claude account bindings)
+  with a number-shaped hash suffix were silently lost on restart — YAML map
+  keys are now quoted on write.
+
 ## [2.9.0] — 2026-06-30
 
 ### Added