fix(setup): canonical-only hook registration, heal-first, PT_EXPLICIT consent provenance

Three root causes of the phantom-AskUserQuestion-hooks class, all in the
registration path:

- Bug A: the Conductor auto-opt-in upgraded PT_DECISION "prompt" -> "yes"
  even when "prompt" was dev-setup's EXPLICIT --plan-tune-hooks=prompt pin,
  so every new Conductor workspace installed hooks. PT_EXPLICIT (flag/env/
  config-key-presence via `gstack-config has`) now gates the auto-opt-in to
  the true silent fall-through.
- Bug B: hook commands were baked from $SOURCE_GSTACK_DIR (`pwd -P` of the
  running tree — ephemeral for worktrees). Registration is now CANONICAL-ONLY
  via _hook_command_path (${CLAUDE_CONFIG_DIR:-$HOME/.claude}/skills/gstack);
  missing canonical hook = skip + log, never a baked tree path. SessionStart
  moves to schema-aware add-event under its identity source; whitespace paths
  are quoted.
- Bug C: nothing ever pruned, and dead tagged entries blocked the
  "already installed" guards forever. Setup now heals FIRST on every run
  (prune-stale --repoint at the stable install), surfaces a one-line summary
  only when something changed, surfaces the plan_tune_hooks:no-vs-live-hooks
  contradiction, and --no-team tears down all three sources plus an identity
  sweep for untagged strays.

dev-setup's no-mutation guarantee gains its stated repair exception (prune
dead / re-point existing, never ADD).

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

bin/dev-setup

@@ -68,10 +68,17 @@ fi
 # GSTACK_PLAN_TUNE_HOOKS=yes would still resolve to "install" and rewrite the
 # user's global ~/.claude/settings.json to point at THIS ephemeral worktree —
 # which breaks once the workspace is deleted. The flag has highest precedence,
-# so it pins resolution to "prompt", and closed stdin then makes prompt-mode a
-# no-op skip (no install, no decline marker). A dev workspace must never mutate
-# global settings.json. To install the hooks, run `./setup --plan-tune-hooks`
-# directly (outside dev-setup). Saved prefix/other config preferences still apply.
+# so it pins resolution to "prompt" (setup's PT_EXPLICIT provenance keeps the
+# Conductor auto-opt-in from overriding an explicit flag), and closed stdin
+# then makes prompt-mode a no-op skip (no install, no decline marker).
+#
+# A dev workspace never ADDS hooks to global settings.json. One stated repair
+# exception: setup's heal-first pass may PRUNE dead gstack hook entries and
+# RE-POINT existing ones at the stable ~/.claude/skills/gstack install —
+# strictly convergent repair, never a new registration, and hook registration
+# itself is canonical-only (an ephemeral tree path can never be baked in).
+# To install the hooks, run `./setup --plan-tune-hooks` directly (outside
+# dev-setup). Saved prefix/other config preferences still apply.
 #
 # GSTACK_SKIP_GBRAIN_REGEN=1 is passed INLINE (not exported) so it scopes to
 # exactly this nested setup call and can't leak into any other setup path. It