fix(sdk): make cleanup reliable and preserve typed tool arguments

[gersmann]

Failed or cancelled requests could retain pending state, concurrent closes could return before cleanup finished, and closed streams could block on another read. Temporary Codex owners could also close live streams, while tool dispatch converted validated nested objects back into dictionaries.

This change makes requests own their cleanup, joins session shutdown through one shielded task, gives streams one exhaustion flag, and retains their originating owner. Cancellation watchers stop when consumption ends, and tool callbacks receive validated Python values directly.

• Stage generated contracts until every generation step succeeds, then publish once.
• Use the same selected commit for next-release tags, wheels, and sdist.
• Remove unread stderr history, thirteen copied service protocols, unused schema-file helpers, and the disconnected schema transformer.
• Add regressions for lifecycle races, structured arguments, generation failures, and release branch advancement; scope ordinary async test clients with the existing context manager.

Validation:

• rtk proxy env RUSTUP_TOOLCHAIN=1.95.0 make lint — passed; editable native package built successfully and all 29 package files passed mypy.
• rtk proxy env RUSTUP_TOOLCHAIN=1.95.0 make test — 266 passed, 2 skipped; 92.02% coverage.
• rtk proxy git diff --cached --check — passed before commit.
• Independent correctness and Ponytail reviews passed.
• Actionlint reports the same existing SC2086 and two outdated runner-label diagnostics as the base revision; no new findings.

Markdown files and generated protocol models are excluded from this PR.

[github-actions]

Codex Autonomous Review:

• Overall: patch is correct
• New findings this run: 0
• Prior unresolved Codex findings still relevant: 0
• Active findings total: 0

No incremental changes since the previously reviewed commit; nothing new to review or flag.

Tip: comment with "/codex address comments" to attempt automated fixes for unresolved review threads.