test: update 2026 interop and conformance pins

[leehack]

Summary

• Re-pin the TypeScript 2026-07-28 RC interop fixture from pkg.pr.new previews to published @modelcontextprotocol/client@2.0.0-beta.1 and @modelcontextprotocol/server@2.0.0-beta.1 packages.
• Update official conformance gates/docs from @modelcontextprotocol/conformance@0.2.0-alpha.7 to 0.2.0-alpha.8.
• Add alpha.8 stateless server diagnostics for missing client capabilities, response-stream shape, and request-scoped logging.
• Align the 2026 client custom-header fixture with alpha.8 expectations by not mirroring the unannotated float_val parameter.
• Refresh conformance/interoperability docs, spec coverage, expected-failure headers, README notes, and changelog entries.

Existing issue / PR check

• No dedicated issue found for the combined conformance-alpha8 / TypeScript beta re-pin work.
• Supersedes test: update MCP conformance to alpha.8 #299; the alpha.8 conformance changes are folded into this PR.

Test Plan

• dart pub get
• dart format --output=none --set-exit-if-changed lib/src/server/mcp_server.dart test/conformance/mcp_2026_07_28_rc_client.dart test/conformance/mcp_2026_07_28_rc_server.dart test/conformance/run_2025_server_conformance.dart test/conformance/run_2026_07_28_rc_client_conformance.dart test/conformance/run_2026_07_28_rc_server_conformance.dart
• git diff --check
• dart analyze
• dart test --reporter compact test/docs/markdown_docs_test.dart test/mcp_2026_07_28_test.dart
• dart run test/conformance/run_2026_07_28_rc_server_conformance.dart --timeout-seconds 90 --output-dir /tmp/mcp-combined-alpha8-server — 40 passed, 0 failed/timeout
• dart run test/conformance/run_2026_07_28_rc_client_conformance.dart --timeout-seconds 90 --output-dir /tmp/mcp-combined-alpha8-client-rerun — 31 passed, 1 expected failure (json-schema-ref-no-deref)
• dart run test/conformance/run_2025_server_conformance.dart --timeout-seconds 120 --output-dir /tmp/mcp-combined-alpha8-2025-server — 49 passed, 0 failed
• (cd test/interop/ts_2026_07_28_rc && npm ci)
• dart run tool/testing/run_ts_2026_07_28_rc_interop.dart — TypeScript beta client -> Dart server and Dart preview client -> TypeScript beta server succeeded

Notes

• One local full 2026 client conformance run had a transient auth/metadata-var2 failure (Client sent an HTTP request to an HTTPS server from the alpha conformance fixture); rerunning that scenario and then the full client suite passed with only the expected json-schema-ref-no-deref fixture gap.
• Local npm emitted unrelated user-level always-auth deprecation warnings while installing TS fixture dependencies; no repo/global config was changed.

[Copilot]

Pull request overview

This PR updates the repository’s MCP 2026-07-28 RC interoperability and conformance fixtures to track newly published upstream artifacts (TypeScript SDK beta packages and MCP conformance alpha.8), and adds new alpha.8 stateless diagnostics/fixtures for capability enforcement, streaming response shape, and request-scoped logging.

Changes:

• Re-pin the 2026-07-28 TypeScript interop fixture from pkg.pr.new previews to published @modelcontextprotocol/client@2.0.0-beta.1 / @modelcontextprotocol/server@2.0.0-beta.1.
• Update conformance runners/docs from @modelcontextprotocol/conformance@0.2.0-alpha.7 to 0.2.0-alpha.8 and refresh expected-failure baselines/docs.
• Add alpha.8 stateless server diagnostic tools and introduce server-side required client capability validation for draft-2026 tools/call.

Reviewed changes

Copilot reviewed 15 out of 16 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/interop/ts_2026_07_28_rc/README.md	Updates fixture documentation to reflect published TypeScript beta pins.
test/interop/ts_2026_07_28_rc/package.json	Switches TypeScript SDK dependencies from pkg.pr.new URLs to 2.0.0-beta.1.
test/interop/ts_2026_07_28_rc/package-lock.json	Updates lockfile to match the published 2.0.0-beta.1 packages.
test/conformance/run_2026_07_28_rc_server_conformance.dart	Bumps default conformance package pin to 0.2.0-alpha.8.
test/conformance/run_2026_07_28_rc_client_conformance.dart	Bumps default conformance package pin to 0.2.0-alpha.8.
test/conformance/run_2025_server_conformance.dart	Bumps default conformance package pin and updates alpha-version commentary.
test/conformance/README.md	Updates command examples and narrative to 0.2.0-alpha.8.
test/conformance/mcp_2026_07_28_rc_server.dart	Adds alpha.8 diagnostic tools (missing capability, stream shape, request-scoped logging).
test/conformance/mcp_2026_07_28_rc_client.dart	Aligns custom-header fixture with alpha.8 expectations (drops float_val).
test/conformance/2026_07_28_rc_expected_failures.txt	Updates header/comments for alpha.8 (server suite now green).
test/conformance/2026_07_28_rc_client_expected_failures.txt	Updates header/comments for alpha.8 (keeps json-schema-ref-no-deref).
lib/src/server/mcp_server.dart	Adds draft-2026 enforcement of tool-required client capabilities via transport-level request validation.
doc/spec-coverage-2026-07-28-rc.md	Updates conformance pin references and refreshes draft coverage notes.
doc/mcp-2026-07-28-rc.md	Updates conformance pin and TypeScript interop pin narrative to beta.1.
doc/interoperability.md	Updates the 2026-07-28 RC interop documentation to reference published beta packages.
CHANGELOG.md	Records the repins and alpha.8 diagnostics additions.

Files not reviewed (1)

• test/interop/ts_2026_07_28_rc/package-lock.json: Generated file

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