feat: named error codes for ports

[parnexcodes]

Closes #24

What

Adds the port_not_found (404), port_limit_reached (409) and ports_unavailable (503) error codes to this SDK's named codes, the same way the connector and image codes were added. README notes that port 2222 is reserved (validation_error) and a Dock exposes at most 10 ports.

Why

Backend returns these codes for the ports API (verified against apps/backend/src/docks/dock-ports.service.ts); SDK users should not need string literals.

How to verify

Run the SDK test suite; the error-code test now covers the three port codes.

Risk

Low. Additive constants/classes and docs only.

🤖 Generated with Claude Code

[parnexcodes]

Review: feat: named error codes for ports

Verdict: SHIP

Checked against usedock/dock main (2fb1128), apps/backend/src/docks/dock-ports.service.ts: ports_unavailable 503 (ServiceUnavailableException), port_limit_reached 409 (ConflictException, MAX_PORTS_PER_DOCK = 10), port_not_found 404 (NotFoundException on remove), and port 2222 in RESERVED_PORTS -> BadRequestException validation_error. Codes, statuses, the 10-port limit and the 2222 claim in the README all match. The SDK does no client-side port validation, so the 2222 error does come from the API.

Naming follows the existing typed-subclass pattern (PortNotFoundError, PortLimitReachedError, PortsUnavailableError), registered in _BY_CODE and exported from usedock. The parametrized test checks code, status and class for all three.

Fixed on the branch (ac78d34): the new names were inserted before Operation/Port in __all__, which is otherwise alphabetical; moved them after Port.

Blocking

None.

Non-blocking

None.

Checks

• ruff check ., ruff format --check ., mypy: pass
• pytest tests/test_client.py: 63 passed, 1 skipped
• CI on ac78d34 (test 3.9/3.13, gitleaks, cla): pass