slice 3.5d: agent_template_link + brain seed helper + skills merge

Ships the lineage layer that ties agents back to their team template
and wires the MCP skills server to actually merge template default
skills with per-agent overrides.

Migration 0050 adds `agent_template_link` (agent_id PK, template_id,
template_version, role_slot, seeded_at, created_at + indexes for
template/role lookups). Populated at agent-materialization time by
Slice 4's mission-launch orchestrator; read here by the skills MCP
server and by future level-up (Slice 8.5).

New Rust surface:
  - cm_db::repo::agent_template_link  (upsert / get / mark_seeded /
    agents_for_template — the last is what level-up's "prompt upgrade
    on template N+1" query needs)
  - cm_api::brain_seed::ingest(claw_id, seed_md, identity_prompt)
    opens cm_brain::ClawBrain on spawn_blocking, sets system_prompt
    on first touch, writes seed as agent_md, commits. Idempotent —
    skips when agent_md already populated.
  - cm_api::mcp_skills::mcp_skills tools/call now resolves the caller
    agent's template + role via agent_template_link and merges
    template default skills with per-agent overrides (was overrides-
    only in Slice 3.5b).
  - cm_api::team_template_loader now binds template_role_skills after
    upserting each template — looks up each declared skill by name,
    attaches with pin_in_context=true for foundation skills and the
    first two role skills. Missing skills log + skip.
  - Boot ordering: skills load BEFORE team templates so the binding
    lookup resolves.

Follow-up (Slice 4): mission-launch orchestrator calls brain_seed::ingest
+ agent_template_link::upsert when minting a team from a template.
Until that lands, the link is populated only by manual writes; the
MCP merge is silent-no-op for agents without a link (falls through
to overrides-only), which matches the pre-3.5d behavior.

Co-Authored-By: Claude Opus 4.7 <[email protected]>

crates/bins/clawmates-server/src/main.rs

@@ -271,23 +271,17 @@ async fn run() -> Result<(), String> {
         runtime.clone(),
         std::time::Duration::from_secs(3),
     );
-    // Load builtin team templates from disk into team_templates +
-    // template_roles. Idempotent per boot; edits to templates/teams/*.toml
-    // go live on the next deploy.
+    // Boot-time content loaders — skills first, then team templates
+    // (Slice 3.5d): the team_template_loader binds template_role_skills
+    // by looking up skills by name, so the skills catalog must be
+    // populated first. Both are idempotent per boot.
     {
         let pool = pool.clone();
         tokio::spawn(async move {
-            let n = cm_api::team_template_loader::load_builtins(&pool).await;
-            eprintln!("team_template_loader: loaded {n} builtin team template(s)");
-        });
-    }
-    // Load builtin skills from skills/**/*.md into the skills catalog
-    // (Slice 3.5c). Same idempotent-per-boot semantics.
-    {
-        let pool = pool.clone();
-        tokio::spawn(async move {
-            let n = cm_api::skills_loader::load_builtins(&pool).await;
-            eprintln!("skills_loader: loaded {n} builtin skill(s)");
+            let n_skills = cm_api::skills_loader::load_builtins(&pool).await;
+            eprintln!("skills_loader: loaded {n_skills} builtin skill(s)");
+            let n_tpl = cm_api::team_template_loader::load_builtins(&pool).await;
+            eprintln!("team_template_loader: loaded {n_tpl} builtin team template(s)");
         });
     }
     // Outbound-email delivery: drains the §15-gated `outbox` over SMTP. Inert