fix: Remove escalation — planner routes through vault instead (#721)

Remove ESCALATED signal and escalation handling from planner, supervisor,
and gardener. When blocked on external resources or human decisions, these
agents now file vault procurement items (vault/pending/*.md) instead of
escalating directly to the human.

Changes:
- Planner formula: ESCALATED signal replaced with HUMAN_BLOCKED; files
  vault items and marks prerequisites as blocked-on-vault
- Supervisor formula/prompt: escalation sections replaced with vault item
  filing; preflight now reports pending vault items instead of escalation
  replies
- Gardener formula: ESCALATE action replaced with VAULT action; files
  vault/pending/*.md for human decisions
- Groom-backlog formula: same ESCALATE→VAULT replacement
- Gardener shell: PHASE:escalate replaced with PHASE:failed for merge
  blocks and CI exhaustion; escalation reply consumption removed
- Supervisor shell: escalation reply consumption removed from both
  supervisor-run.sh and legacy supervisor-poll.sh
- Prerequisite tree: #466 updated from "escalated" to "blocked-on-vault"

The vault is the factory's only interface to the human for resources and
approvals. Dev/action agents retain PHASE:escalate for operational session
issues (CI timeouts, merge blocks) which are a different mechanism.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

formulas/run-gardener.toml

@@ -119,8 +119,16 @@ DUST (trivial — single-line edit, rename, comment, style, whitespace):
   Do NOT close dust issues — the dust-bundling step auto-bundles groups
   of 3+ into one backlog issue.
 
-ESCALATE (needs human decision):
-  printf 'ESCALATE\n1. #NNN "title" — reason (a) option1 (b) option2\n' >> "$RESULT_FILE"
+VAULT (needs human decision or external resource):
+  File a vault procurement item at $PROJECT_REPO_ROOT/vault/pending/<id>.md:
+    # <What decision or resource is needed>
+    ## What
+    <description>
+    ## Why
+    <which issue this unblocks>
+    ## Unblocks
+    - #NNN — <title>
+  Log: echo "VAULT: filed vault/pending/<id>.md for #NNN — <reason>" >> "$RESULT_FILE"
 
 CLEAN (only if truly nothing to do):
   echo 'CLEAN' >> "$RESULT_FILE"
@@ -150,7 +158,7 @@ Sibling dependency rule (CRITICAL):
 
    Only close for clear, unambiguous violations. If the issue is
    borderline or could be interpreted as compatible, leave it open
-   and ESCALATE instead.
+   and file a VAULT item for human decision instead.
 
 8. Quality gate — backlog label enforcement:
    For each open issue labeled 'backlog', verify it has the required
@@ -178,7 +186,7 @@ Processing order:
   2. AD alignment check — close backlog issues that violate architecture decisions
   3. Quality gate — strip backlog from issues missing acceptance criteria or affected files
   4. Process tech-debt issues by score (impact/effort)
-  5. Classify remaining items as dust or escalate
+  5. Classify remaining items as dust or route to vault
 
 Do NOT bundle dust yourself — the dust-bundling step handles accumulation,
 dedup, TTL expiry, and bundling into backlog issues.