feat: graceful run termination reports real results on abort (#36)

[schplitt]

Closes #36.

Problem

Aborting a run destroyed the socket; Rust saw EOF and reclaimed the isolate but never sent a Result frame, so the TypeScript side fabricated the aborted RunResult (durationMs: 0, cpuTimeMs: 0, bridgeCalls: []). Because durable-isolates suspension is implemented as an abort, every suspension lost its timings and per-call bridge records.

Approach

• TS sends the existing Terminate frame (0x07) carrying the run ID instead of tearing the socket down.
• Rust, parked in the run's bridge-wait poll loop (exactly where a suspension sits — awaiting a bridge response), consumes Terminate, terminate_execution()s, and returns a real ERR_ABORTED Result with durationMs, cpuTimeMs, and the bridge-call records collected so far.
• TS waits a short grace period (100 ms). On success the connection stays healthy and is reused (no reconnect); index.ts remaps the ERR_ABORTED Result to status: 'aborted' with the abort reason, keeping the telemetry. If no Result arrives (sandbox stuck in a tight synchronous loop, so Rust never reaches the frame read), it falls back to today's socket teardown + synthesized zeros.

Prompt interruption of a purely CPU-bound (busy) isolate stays deferred per DESIGN.md §14.7 — the CPU guard remains the backstop; a code comment at the poll-loop site documents this.

Changes

• Rust: parse_terminate_payload (ipc.rs); RunError::Aborted + poll-loop Terminate handling (v8.rs); ERR_ABORTED/AbortError mapping (wire.rs); session main-loop now ignores a stray Terminate instead of closing (keeps the slot poolable).
• TS: encodeTerminatePayload (ipc.ts); graceful terminate + grace/fallback in drainUntilResult (client.ts); graceful-abort remap in index.ts; stale-comment fixes in types.ts.
• Docs: protocol.md (ERR_TERMINATED → ERR_ABORTED), DESIGN.md §5.2/§14.7; changeset (minor).

Testing

• Rust: 211 passed — incl. new terminate_frame_aborts_run_with_telemetry, parse_terminate_payload, aborted_maps_to_err_aborted.
• TS: 454 passed / 1 skipped — converted the "aborted runs carry no bridge report" test to assert graceful telemetry; added global + import-leaf abort-telemetry coverage.
• pnpm fmt:native:check, pnpm lint, pnpm typecheck clean.

Note: pnpm lint:native (clippy -D warnings) reports 15 pre-existing warnings in untouched code (dead-code/complexity lints); this diff adds none.