fix: Address review — remove stale Matrix references from runtime prompts

Critical fixes:
- vault/vault-agent.sh: Update comment and prompt to use PHASE:escalate
  instead of "send a Matrix message"
- dev/dev-agent.sh: Update escalation instruction from "reply via Matrix"
  to "respond via the forge"
- dev/phase-handler.sh: Update build_phase_protocol_prompt() escalation
  text from "reply via Matrix" to "respond via the forge"

Minor fixes:
- bin/disinto: Remove duplicate comment line in docker-compose header
- README.md: Update vault table row from "via Matrix" to "via vault/forge"
- BOOTSTRAP.md: Remove "Matrix credentials" from TOML description
- lib/AGENTS.md: Remove "callers may follow up via Matrix" from
  formula_phase_callback description

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

README.md

@@ -153,7 +153,7 @@ disinto/
 | **Review** | Every 10 min | Finds PRs without review, runs Claude-powered code review, approves or requests changes. |
 | **Gardener** | Daily | Grooms the issue backlog: detects duplicates, promotes `tech-debt` to `backlog`, closes stale issues, escalates ambiguous items. |
 | **Planner** | Weekly | Updates AGENTS.md documentation to reflect recent code changes, then gap-analyses VISION.md vs current state and creates up to 5 backlog issues for the highest-leverage gaps. |
-| **Vault** | Every 30 min | Safety gate for dangerous or irreversible actions. Classifies pending actions via Claude: auto-approve, auto-reject, or escalate to a human via Matrix. |
+| **Vault** | Every 30 min | Safety gate for dangerous or irreversible actions. Classifies pending actions via Claude: auto-approve, auto-reject, or escalate to a human via vault/forge. |
 
 ## Design Principles