feat(fleet): inject persona contract at launch (A3b) (#664)

packages/mosaic/src/fleet/persona-contract.ts

@@ -0,0 +1,63 @@
+/**
+ * Persona-contract injection at launch (North Star A3b).
+ *
+ * A spawned fleet agent should boot already knowing WHO it is: its class's role
+ * contract (mandate + boundaries). The companion goal A3a exports the agent's
+ * resolved class into the pane env as `MOSAIC_AGENT_CLASS`; here we read that
+ * class at launch (composeContract → system prompt) and inject the resolved
+ * persona contract so the identity is resident from the agent's first turn.
+ *
+ * OVERRIDE-AWARE: resolution goes through fleet-personas' resolver, so a
+ * user-customized persona in the PRESERVE-protected `fleet/roles.local/` layer
+ * WINS over the baseline `fleet/roles/` of the same class. That is the
+ * launch-time proof of AC-NS-7 — a customized persona actually reaches the model
+ * when the agent boots, not just in `mosaic fleet persona show`.
+ *
+ * Tolerant by contract (mirrors readFleetCommsBlock): an empty/missing class, an
+ * unknown class, or a missing role file all yield '' so the launcher no-ops
+ * silently. This MUST never throw during launch.
+ *
+ * Standalone module (no fleet.ts import) to keep launch.ts's prompt path free of
+ * the heavy fleet command module; it depends only on the lightweight persona
+ * resolver.
+ */
+
+import {
+  resolvePersonaSync,
+  defaultRolesDir,
+  defaultOverrideDir,
+} from '../commands/fleet-personas.js';
+
+/**
+ * Resolve `klass`'s persona contract (override-aware) and render it as a
+ * clearly-delimited launch block. Returns '' on any miss (falsy class, unknown
+ * class, missing/unreadable file) so composeContract can push it unconditionally
+ * and have it no-op silently. Never throws.
+ */
+export function readPersonaContractBlock(mosaicHome: string, klass: string | undefined): string {
+  if (!klass || !klass.trim()) return '';
+  let resolved: ReturnType<typeof resolvePersonaSync>;
+  try {
+    resolved = resolvePersonaSync(klass.trim(), {
+      rolesDir: defaultRolesDir(mosaicHome),
+      overrideDir: defaultOverrideDir(mosaicHome),
+    });
+  } catch {
+    // Best-effort onboarding: a resolver hiccup must not abort the launch.
+    return '';
+  }
+  if (!resolved) return '';
+
+  const layerNote =
+    resolved.layer === 'override'
+      ? '_(resolved from the `fleet/roles.local/` override layer — wins over baseline)_'
+      : '_(resolved from the baseline `fleet/roles/` layer)_';
+
+  return `# Persona Contract (${resolved.klass})
+
+${layerNote}
+
+You are operating as the **${resolved.klass}** persona. The role contract below is your identity — its mandate and boundaries govern what you own and what you must not do for this assignment.
+
+${resolved.content.trim()}`;
+}