feat: identity app surface — W1: remove nb__manage_app

[mgoldsborough]

First slice of the identity app surface effort (stacked on #272 / stage-2/main; retarget to main if #272 merges first). This branch will accumulate the rest of the work — global tool dispatch (W3), identity host path + root /conversations route (A3/A4), and the Files/Automations migrations (Phases B/C). Design + sign-off live in nimblebrain-ops/research/delegation-model/IDENTITY_APP_SURFACE.md.

W1 — remove nb__manage_app

The conversational bundle install/uninstall/configure chat tool is removed (signed off), not redesigned. It was non-functional today, and conversational workspace mutation deserves real design later (single tool, explicit workspace param, per-call admin auth). The underlying install lifecycle, nb CLI, Apps catalog, and connector config UI are all unaffected.

Changes

• system-tools.ts — drop the manage_app tool def + the configureBundle / installBundleInWorkspaceViaCtx / uninstallBundleFromWorkspaceViaCtx helpers + ManageBundleContext. gate / manageBundleCtx become reserved positional slots (_gate / _manageBundleCtx) so every call site's arity holds (the file's reserved-slot convention).
• runtime.ts — drop the manageBundleCtx construction + its call-site arg.
• features.ts / privilege.ts — drop the manage_app feature-map entries and privilege rule. The bundleManagement flag is kept as a reserved operator config knob for the bundle-management tool the design contemplates reintroducing.
• bootstrap.md / skill-authoring.md — install and credential setup now happen in the Apps catalog / CLI, not chat.
• CLI deprecation strings + stale comments across startup.ts, workspace-ops.ts, connector-tools.ts, workspace-credentials.ts repointed off manage_app.

Dead-code cleanup (addresses QA review)

Removing manage_app orphaned two helpers whose only caller was the deleted uninstallBundleFromWorkspaceViaCtx:

• resolveBundleServerName (system-tools.ts) and uninstallBundleFromWorkspace (workspace-ops.ts) are both deleted — they had zero production callers after W1.
• The canonical uninstall is BundleLifecycleManager.uninstall(), which is self-contained (resolves the server name via its instance map, runs the protected check, removes the source, clears workspace credentials, unregisters placements/config/automations). It never called either helper.
• installBundleInWorkspace is kept — it's still live (connector install at connector-tools.ts).

Tests

• Delete the two manage_app-only integration files (configure-credentials, bundles-workspace-bundle-mgmt) and the two unit files that pinned the now-deleted helpers (workspace-ops-uninstall, workspace-uninstall-credentials).
• The live uninstall behaviors are covered against lifecycle.uninstall() in lifecycle.test.ts: protected reject, credential file removal + sibling untouched, data-dir preservation, idempotent no-op.
• Repoint the privilege / audit / role-visibility tests to the surviving skills__create gate; assert nb__manage_app is absent.

Verification

• verify:static clean (format, lint, tsc, cycles, code-style, codegen).
• Unit 3069 / web 311 pass.
• Integration 605 pass / 3 fail — the 3 are pre-existing instructions-rework failures (a separate compose.ts Layer-2-overlay bug), unchanged by this PR.

Follow-ups (not in this PR)

• schemas.nimblebrain.ai (products/nimblebrain/schemas) still describes bundleManagement / protected in terms of nb__manage_app. That schema is fetched into src/config/nimblebrain-config.schema.json on postinstall, so it can't be fixed here.
• forcePrompt on the credential resolver no longer has a caller (it was manage_app configure's); kept as a generic capability.