feat(session): persist model tier overrides per session

Store per-session config in SQLite and route /model and /reset through command fast-paths so channel sessions keep independent model selection across reconnects and restarts.

src/config/schema.ts

@@ -108,6 +108,15 @@ const skillsLoadSchema = z.object({
   watch_debounce_ms: z.number().min(10).max(10_000).default(250),
 }).default({});
 
+const skillsShellRunnerGovernanceSchema = z.object({
+  /** Responsible owner for shell-runner allowlist decisions. */
+  owner: z.string().min(1).optional(),
+  /** Review cadence for allowlist + rollout status checks. */
+  review_cadence_days: z.number().min(1).max(90).default(7),
+  /** Minimum success rate required before broader rollout. */
+  promotion_min_success_rate: z.number().min(0).max(1).default(0.9),
+}).default({});
+
 const skillsSchema = z.object({
   /** Directory for user-created workspace skills. */
   workspace_dir: z.string().optional(),
@@ -115,6 +124,14 @@ const skillsSchema = z.object({
   managed_dir: z.string().optional(),
   /** Directory for bundled skills shipped with Flynn. */
   bundled_dir: z.string().optional(),
+  /** Global policy gate for installer command execution. */
+  installation_execution: z.enum(['disabled', 'enabled']).default('disabled'),
+  /** Allow use of the shell runner for installer commands. */
+  allow_shell_runner: z.boolean().default(false),
+  /** Allowlist patterns for shell runner commands (supports '*' wildcard). */
+  shell_runner_allowlist: z.array(z.string()).default([]),
+  /** Governance controls for shell-runner rollout decisions. */
+  shell_runner_governance: skillsShellRunnerGovernanceSchema,
   /** Skills watcher settings. */
   load: skillsLoadSchema,
 }).default({});