feat: clear auto-stop on resume; size-check file read/list

[parnexcodes]

Closes #20
Closes #19

What

• docks.resume(ttl_seconds=UNSET): omitted keeps the current value, None sends ttlSeconds: null (clears auto-stop), a number sets it. Same pattern as update.
• files.read, files.read_bytes and files.list check the UTF-8 byte length of the final command and raise DockError("file_too_large", 0, ...) before sending when it exceeds 64 KB.
• README updated.

Why

Backend (usedock/dock #75) now accepts ttlSeconds on resume (number sets, null clears, absent keeps). An over-long path previously produced an opaque API error on read/list; dock-js and dock-go already refuse locally.

How to verify

Run in a venv: ruff check . && ruff format --check . && mypy && DOCK_SCENARIOS_DIR=<dock>/sdk-scenarios DOCK_SCENARIOS_REQUIRED=1 pytest -rs

• ruff, ruff format, mypy: pass.
• New tests: resume unset/null/number body shapes; read/read_bytes/list over the limit with a multibyte path raise file_too_large with zero requests sent.

Risk

Low. resume(ttl_seconds=None) now sends null instead of omitting (intended). The size check only rejects commands the API would reject anyway.

After rebasing on main (SCENARIOS_REF 05d0182), all offline scenarios pass, including list-connectors and list-images.

🤖 Generated with Claude Code

[parnexcodes]

Review: feat: clear auto-stop on resume; size-check file read/list

Verdict: SHIP

Rebased on origin/main (after #18: connectors/images, SCENARIOS_REF 05d0182). One conflict in tests/test_client.py, resolved by keeping both sides; client.py, README and SCENARIOS_REF merged cleanly. Force-pushed as 963b79f.

Verified against the backend at usedock/dock 51d3036 (#75): ResumeDockDto.ttlSeconds is @IsOptional with number | null, and DocksService.resume writes ttlSeconds only when it is not undefined (null clears, absent keeps). resume(ttl_seconds=UNSET) matches this and matches update and dock-js (compact drops only undefined, so null is sent). The read/list commands are byte-identical to dock-js readCommand/listCommand, and _check_size counts UTF-8 bytes against the same 64 KB limit as assertCommandSize, with file_too_large, status 0 and nothing sent.

Blocking

None.

Non-blocking

1. PR body "How to verify" still reports 2 failing scenarios (list-connectors, list-images). After the rebase, all offline scenarios pass against SCENARIOS_REF. Update the body.
2. README.md:51 says "files.read and files.list"; read_bytes is covered too. Mention it if you want the README complete.

Checks

• ruff check ., ruff format --check .: pass
• mypy: pass (4 source files)
• pytest -rs with DOCK_SCENARIOS_DIR at usedock/dock 05d0182 and DOCK_SCENARIOS_REQUIRED=1: 98 passed, 9 skipped (8 live scenarios without credentials, 1 CI-only). All 8 offline scenarios pass, including list-connectors and list-images.
• Mutation check: with the base client.py, all 4 new tests fail. The multibyte path (40003 chars, about 80 KB) also catches a check that counts characters instead of bytes.
• CI after the rebase: test 3.9/3.13, gitleaks, cla all pass.