The NY-Summit AgentCore Harness CFN type is now public in all regions, so the
harness summit-preview features can be ungated. This removes the
ENABLE_GATED_FEATURES gate at the in-scope call sites only — knowledge-base,
gateway passthrough, and config-bundle branch stay gated (they were not part of
this ungating).

Ungated:
- AWS Skills: --aws-skills source on `add skill` and the TUI skill-source picker
  (no longer "Coming soon").
- Managed memory: the managed/existing/disabled memory-mode union and the
  managed-tuning flags. The legacy "No persistent memory" enabled/disabled TUI
  screen is removed; the auto-created `${name}Memory` sibling is gone. "No memory"
  (--no-memory / --memory-mode disabled) now writes { mode: 'disabled' }, which
  maps to CFN Memory: { Disabled: {} } — a true opt-out instead of silently
  getting a service-auto-created memory.
- Harness Version: `status` and the deploy drift note show the config version
  unconditionally.

Fixes found while testing (in-scope):
- Reject --no-memory combined with managed-only flags (--memory-strategies /
  --memory-event-expiry-days / --memory-encryption-key-arn) instead of silently
  dropping them.
- TUI existing-memory retrieval tuning (messages count / topK / relevance) was
  silently dropped; the wizard setters now write into the memory union and the
  add/create flows share one toMemoryAddOptions() translation helper.
- `deploy --json` no longer emits the managed-memory heads-up notice to stdout
  (it corrupted the JSON output); the notice is suppressed under --json and still
  recorded in the deploy log.

Tests: ungated and corrected the integ memory-mode coverage (removed the legacy
auto-memory assertions); added unit coverage for memory-mode resolution and the
TUI translation helper; added harness-managed-memory and harness-aws-skills e2e
suites (deploy -> invoke -> memory round-trip / skills-loaded -> teardown),
verified against a real account. 5425 unit tests pass; typecheck + lint clean.

Depends on aws/agentcore-l3-cdk-constructs#289.

…ory validation

Round-5 bug-bash follow-ups for the opt-in memory default.

Help/notice text (was still describing the old managed-is-default behavior):
- `--memory-mode` help: "disabled (default), managed, or existing" (was "managed (default), ...").
- `--no-memory`/`--memory-name`/`--memory-arn` and `create --no-harness-memory` help: drop the
  "auto-creating" framing (nothing is auto-created; memory is opt-in).
- MANAGED_MEMORY_DEPLOY/ADD_NOTICE: no longer call managed "the default"; phrase as "you requested
  --memory-mode managed".
- Refresh the stale "managed is the default" source comment in HarnessPrimitive.add.

Validation (reject instead of silently doing the wrong thing):
- `--memory-arn`/`--memory-name` + `--memory-mode managed|disabled` → conflict error (was silently
  downgraded to existing).
- existing-only tuning flags (--memory-actor-id/--memory-messages-count/--memory-top-k/
  --memory-relevance-score) given with no existing reference → error (were silently dropped).
- `--memory-arn` is now format-validated (was accepted unvalidated).

Other robustness (pre-existing, surfaced by the bug bash):
- formatError no longer dumps the raw JS stack trace to users by default (set AGENTCORE_DEBUG=1 to
  see it) — config/validation errors were leaking minified dist frames.
- create: route `--memory` (an agent-only option) to the agent path so it conflicts with harness-only
  flags instead of being silently ignored on the harness path.
- TUI useMultiSelectNavigation: on confirm, drop selections for options no longer visible in `items`
  (switching memory mode after toggling "Memory tuning" left a stale selection that pushed a
  non-existent step and corrupted wizard navigation).

Tests added/updated for all of the above. 5451 unit tests pass; typecheck + lint clean.