refactor: relocate agent-system/ to .agents/ with 7-role workflow restructure

Moves the agent workflow system from agent-system/ to .agents/ (dotfile convention).
Restructured from 5-role to 7-role pipeline: adds Analyst and splits Reviewer into
Code Reviewer + Security Reviewer. Removes all old workflow run artifacts.

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

.agents/prompts/reviewer-security.md

@@ -0,0 +1,34 @@
+# Security Reviewer Prompt Baseline
+
+Goal:
+- verify the change does not introduce security vulnerabilities or weaken existing protections
+
+Input:
+- code diff
+- `execution-report.json`
+- `plan.json`
+
+Required references:
+- `.agents/checks/guard-catalog.json` (guards where `reviewer` = `security`)
+
+Output:
+- valid JSON by `.agents/contracts/reviewer-security.schema.json`
+
+Scope — verify these guards:
+- GR-SEC-001: CSRF token on POST
+- GR-SEC-002: no PII/secrets in logs or audit metadata
+- GR-SEC-003: SQL via prepared statements only
+- GR-SEC-004: no external CDN or remote asset loading
+- GR-SEC-005: encryption only via Crypto.php
+- GR-SEC-006: file uploads stored in storage/ only
+- GR-SEC-007: API must not start sessions
+- GR-SEC-008: server-side authorization enforced
+- GR-SEC-009: server-side tenant scope enforced
+
+Rules:
+- findings MUST reference a GR-SEC-* guard ID
+- findings MUST include file path and line range where possible
+- severity MUST reflect actual exploitability: `critical` = exploitable in production, `high` = likely exploitable, `medium` = defense-in-depth gap, `low` = minor hardening
+- use `fail` verdict for any `critical` or `high` finding
+- skip guards not relevant to the change (e.g. skip GR-SEC-005 if no crypto touched)
+- for multi-tenant data flows, trace the query path from action → service → repository and verify tenant_id filtering at every level