ci: smoke-test client CLI path and fix everything-client core drift

[canardleteer]

Wire the existing client CLI subcommand into CI (--suite core) and fix two drifts in examples/clients/typescript/everything-client.ts that block core client scenarios (elicitation-sep1034-client-defaults, sse-retry).

Fixes #345.

Motivation and Context

CI runs npm test (vitest) but never exercises the documented client-mode CLI path (node dist/index.js client --command "…"). Regressions in the bundled reference client are only caught when someone runs that path manually against the in-repo fixture (README.md, CONTRIBUTING.md). SDK_INTEGRATION.md documents the same CLI for external SDK conformance clients; it does not validate the in-repo everything-client, so following it would not catch this drift either.

Two concrete examples on current main in --suite core:

1. elicitation-sep1034-client-defaults — handler registered under the wrong name (elicitation-defaults) and outdated elicitation.applyDefaults capability (should be elicitation.form.applyDefaults).
2. sse-retry — no handler registered in everything-client.

The scenario implementations and checks appear correct; upstream typescript-sdk's conformance client already registers both handlers with the correct names and capability shapes.

Related (not in scope for #345): #250 proposes eventually removing vendored examples/{clients,servers}/typescript/ and running CI via sdk typescript-sdk@<pinned-sha>. That is not implemented today; this PR is the incremental fix for the current documented workflow.

How Has This Been Tested?

• npm run build
• npm test (existing vitest)
• npm run test:client-smoke (new — core client scenarios via CLI subprocess path, including elicitation and sse-retry)
• node dist/index.js client --command "npx tsx examples/clients/typescript/everything-client.ts" --scenario elicitation-sep1034-client-defaults — exit 0; all client-elicitation-sep1034-* checks SUCCESS
• node dist/index.js client --command "npx tsx examples/clients/typescript/everything-client.ts" --scenario sse-retry — exit 0; all client-sse-retry-* checks SUCCESS

Validated on canardleteer/conformance by temporarily enabling the CI workflow on dev branch pushes (not included in this PR — upstream ci.yml only triggers on main or pull_request):

Branch	Commit	CI run	Result
dev/canardleteer/ci-client-smoke (+ temp trigger)	c5ec396 + smoke wiring	Actions run #27665693080	Pass — test:client-smoke 246/246 checks, then vitest
dev/canardleteer/ci-client-smoke-baseline (+ temp trigger, no fixture fix)	main + smoke wiring only	Actions run #27665749861	Fail on npm run test:client-smoke (exit 1)

Baseline failure (without fixture fixes), from run #27665749861:

Unknown scenario: elicitation-sep1034-client-defaults
Unknown scenario: sse-retry

✗ elicitation-sep1034-client-defaults: 0 passed, 5 failed
✗ sse-retry: 0 passed, 1 failed
Total: 238 passed, 6 failed, 0 warnings

The baseline branch demonstrates that client-smoke CI catches the drift; npm test alone would still pass on main because it never runs the client CLI path.

Breaking Changes

None.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling (N/A — harness wiring and reference fixture only)
• I have added or updated documentation as needed

Additional context

• package.json: add test:client-smoke — runs node dist/index.js client --command "npx tsx examples/clients/typescript/everything-client.ts" --suite core --timeout 60000 (reuses the existing CLI runner per AGENTS.md; no parallel entry point).
• .github/workflows/ci.yml: run npm run test:client-smoke after npm run build.
• examples/clients/typescript/everything-client.ts:
  • Register handler as elicitation-sep1034-client-defaults (matches scenario name and CLI MCP_CONFORMANCE_SCENARIO).
  • Advertise elicitation.form.applyDefaults: true (required by @modelcontextprotocol/sdk 1.29+ for default merging).
  • Register sse-retry handler (calls test_reconnection; mirrors upstream typescript-sdk fixture).
• examples/clients/typescript/elicitation-defaults-test.ts: delete. This was a standalone one-off client for the elicitation-defaults scenario, never referenced by CI, vitest, or the documented client CLI workflow in CONTRIBUTING.md (which runs scenarios via everything-client.ts). That conflicts with repo guidance in AGENTS.md: passing examples belong in everything-client.ts, not separate client files, and unused example clients should be removed. The elicitation coverage now lives in everything-client.ts under the correct scenario key (elicitation-sep1034-client-defaults); keeping the orphan file would leave a second, stale copy still advertising the old elicitation.applyDefaults capability shape.

No scenario or check changes.