feat(spec-phase): surface zero-classification edge-probe requirements as unclassified candidates (#1110) (#1117)

Edge-probe now surfaces a zero-classification requirement (non-empty prose, no
shape cue matched, no `shapes` override) as a single soft `unclassified — review
manually` candidate instead of silently dropping it — the exact blind spot the
probe exists to catch. Dismissible like any edge; the `shapes: []` opt-out stays
silent; `TAXONOMY` (the closed 8 categories) is unchanged. Under `--auto` the
candidate is left `unresolved`, never auto-`backstop` (a missing shape is not
evidence an edge exists).

Closes #1110

tests/workflow-size-baseline.json

@@ -72,7 +72,7 @@
   "ship.md": 24388,
   "sketch-wrap-up.md": 14223,
   "sketch.md": 19960,
-  "spec-phase.md": 27589,
+  "spec-phase.md": 28438,
   "spike-wrap-up.md": 15092,
   "spike.md": 24517,
   "stats.md": 6718,