runtime: fix component-model audit findings

[lannbot]

Summary

Fix the ten outstanding correctness findings from the Component Model audit, plus the related borrow-to-own guard:

• Enforce guest resource type identity and ownership before consuming host wrappers; retain overlapping host borrows and defer disposal until the final borrower releases.
• Run guest destructors through fresh synchronous tasks/threads without disturbing the dropping activation's context or host driver state.
• Retire removed stream/future endpoints when validation traps, preserve the original error, and always notify drop observers.
• Make synchronous subtask cancellation wait for resolution rather than a STARTED progress event.
• Correct the pinned FACT generator's source string byte limit before guest realloc, using a checked adapter-only immediate rewrite with pin/pattern guards and no new dependency.
• Separate host future read/write busy state; cancel the whole writeAll operation; release untaken owned stream elements and preserve producer/cleanup error attribution.
• Only accept structured validation errors as conformance invalid-component verdicts.

Regression coverage includes translated components for resource identity/lifetimes, destructor context, future round trips, stream ownership, and all string encoding/tag combinations. Other tests cover cancellation state transitions, byte-buffer retirement, failure cleanup, and harness classification.

Based on current main including #315 and #316. #315 already fixed the audit's delayed task.return finding; its behavior is preserved. Existing documented feature exclusions and named spec divergences are unchanged. No protocol, golden transcript, dependency lock, or package version changes.

Verification

• Runtime: 827 passed, 0 failed, 3 existing deferred tests.
• Seeded runtime: 824 passed for each of seeds 1 and 4242, with 6 existing skips each.
• Conformance: 1,285 passing commands, 126 existing xfails, 95 pending, 5 unsupported directives; no new exclusions.
• All 32 host-ABI convention tests pass with byte-identical golden transcripts.
• Independent reviews approved all six tracks after cleanup-error revisions.
• Full just gates < /dev/null: passed, including packaging/npm, pinned shell lanes, Chromium/Firefox page and worker realms, OPFS, and TLS/C0 consumer smokes. Redirecting stdin matches CI's non-TTY environment for the WASI terminal test.
• Consumer worktrees retain their pre-gate status. WAT fixtures regenerate byte-identically.