runtime: fix future cleanup and adapter cache writes

[lannbot]

Summary

Fix the three reproduced P2 defects from the documentation follow-up triage:

• Public Future disposal contains synchronous pump errors and observes deferred disposal-chain rejections, while preserving recorded guest/read failures. Cancel uses the same no-throw boundary discipline.
• Future producer pumps release top-level owned payloads that were lowered but not consumed. Internal write progress distinguishes abandonment/failure from consumed values, with exactly-once cleanup and primary-error preservation.
• Directory-cache puts create parent directories for validated full adapter paths, preserving the existing storage layout and cache keys.

Regression coverage includes validated translated future lifecycle fixtures, plain/JSPI public disposal, cancellation controls, resource registry/destructor observations, source-progress error seams, and a real adapter-bearing cold/warm cache round trip with execution from cached artifacts.

Update the owned-future cleanup contract and remove resolved directory-cache limitations from deployment docs. No package, protocol, lockfile, golden, cache-layout, or expectation-version changes.

Not included: unresolved abstract resource identity, recursive compound-argument cleanup policy, synthetic-only poison listener hardening. Source-buffer consumption remains distinct from transactional destination commitment; this patch does not redesign destination-side failure ownership.

Verification

• Independent cache and future reviews approved the finalized diff.
• Original triage reproductions now pass: 12 future cases and both cache controls.
• Runtime: 853 passed, 0 failed, 3 existing deferred tests.
• Seeded runtime: 850 passed for each of seeds 1 and 4242, with 6 existing skips each.
• Additional independent future + conventions run: 88 passed, unchanged goldens.
• Full just gates < /dev/null passed, including packaging/npm, shell/browser realms, OPFS, and TLS/C0 consumer smokes. Consumer trees retain their initial status.
• WAT fixtures regenerate byte-identically; formatting and diff checks pass.