feat(phase-4a): groups sync + X-Project-Key header substrate

Foundational work for the upcoming group-scoped sharing feature.

Schema (migration 0003_groups.sql + drizzle schema):
  - memory_access enum ('ro' | 'rw') reserved for Agent B's project_shares
  - groups (id, oidc_iss, name, display_name, …) keyed by (oidc_iss, name)
    so different IdPs can both have e.g. "platform" without colliding
  - user_groups (user_id, group_id, synced_at) PK (user_id, group_id)

Auth (auth.ts + lib/auth/sync-groups.ts):
  - jwt callback now syncs `profile.groups` after upserting the user
  - syncUserGroupsFromClaim runs in a single tx: upserts each group,
    inserts new memberships, deletes ones no longer in the claim
  - missing/empty claim → user has zero groups (wipe memberships)
  - EntraID GUID-vs-name edge case: we treat whatever strings the claim
    emits as names verbatim; groups overage (>200 groups → no claim)
    is documented as unsupported in v1

UserContext + JWT (lib/mcp/context.ts, lib/auth/jwt.ts):
  - AuthenticatedClaims.groups surfaced from verified JWT payload
  - UserContext.groups: string[] — live from OIDC token claim, falls
    back to DB snapshot for CLI (HMAC) tokens which carry no claim
  - UserContext.defaultProjectKey: optional, set from header

MCP route (app/api/mcp/route.ts):
  - reads X-Project-Key header, validates against ProjectKey Zod schema,
    400 on invalid; empty/missing leaves defaultProjectKey undefined
  - auto-upserts the header-supplied project so first-use works without
    a separate project.identify call

Tools (lib/mcp/tools.ts):
  - withDefaultProject helper injects ctx.defaultProjectKey when the
    caller omits `project`. Per-tool defaultScope hint avoids breaking
    snippet.put (user-scope default) while making memory.write
    (project-scope default) honor the header
  - applied to memory.write/list/search/update and all snippet.* tools

Web UI:
  - /settings/groups debug page lists current memberships with synced_at
    and a clear empty state pointing at README troubleshooting
  - /settings/tokens grows a "Pin to project" dropdown; selected key is
    baked into the generated `claude mcp add` snippet as
    `--header "X-Project-Key: <key>"`. The JWT itself stays
    identity-only — pinning is purely a UX shortcut
  - settings landing page links to /settings/groups
  - README troubleshooting bullet covers the empty-groups path for
    Authentik / EntraID / Keycloak

Refactor:
  - extracted resolveProjectId + upsertProject from memory-actions.ts
    into lib/projects.ts so the MCP route can reuse upsertProject

Verification:
  - pnpm typecheck clean
  - SKIP_ENV_VALIDATION=true pnpm build clean; /settings/groups in route table

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/lib/auth/jwt.ts

@@ -40,6 +40,14 @@ function jwks() {
 export interface AuthenticatedClaims extends JWTPayload {
   sub: string;
   iss: string;
+  /**
+   * Group names from the OIDC `groups` claim. Authentik / Keycloak / properly-
+   * configured EntraID emit `string[]` here. We coerce non-array / non-string
+   * entries away and present an empty array if the claim is absent. For CLI
+   * (HMAC) tokens this is always undefined — the consumer (userContextFromClaims)
+   * falls back to the DB snapshot from the user's last interactive sign-in.
+   */
+  groups?: string[];
 }
 
 export class UnauthorizedError extends Error {
@@ -52,6 +60,23 @@ export class UnauthorizedError extends Error {
   }
 }
 
+/**
+ * Pull `groups` off a verified OIDC payload as a clean `string[]`. Non-
+ * string entries are dropped silently. Returns undefined when the claim
+ * is absent so callers can distinguish "no claim emitted" from "user is
+ * in zero groups" (`[]`).
+ */
+function extractGroupsClaim(payload: JWTPayload): string[] | undefined {
+  const raw = (payload as { groups?: unknown }).groups;
+  if (raw === undefined || raw === null) return undefined;
+  if (!Array.isArray(raw)) return [];
+  const out: string[] = [];
+  for (const v of raw) {
+    if (typeof v === "string" && v.trim().length > 0) out.push(v.trim());
+  }
+  return out;
+}
+
 function buildWwwAuthenticate(error?: string, description?: string): string {
   const parts: string[] = [`Bearer realm="OAuth"`];
   // RFC 9728 — point clients at our protected-resource metadata so they can
@@ -82,7 +107,9 @@ export async function authenticateBearer(authHeader: string | null): Promise<Aut
       const claims = await verifyCliToken(token);
       // CLI tokens carry the user's real Authentik identity in oidc_iss /
       // oidc_sub. Surface those on the standard claims shape so user
-      // context resolution is identical to the Authentik path.
+      // context resolution is identical to the Authentik path. CLI tokens
+      // never carry a groups claim — leave `groups` undefined; the user-
+      // context resolver falls back to the DB snapshot.
       return {
         ...claims,
         iss: claims.oidc_iss,
@@ -100,7 +127,7 @@ export async function authenticateBearer(authHeader: string | null): Promise<Aut
         buildWwwAuthenticate("invalid_token", "missing sub"),
       );
     }
-    return payload as AuthenticatedClaims;
+    return { ...payload, groups: extractGroupsClaim(payload) } as AuthenticatedClaims;
   } catch (err) {
     if (err instanceof UnauthorizedError) throw err;
     const desc =