fix(ship): preserve quoted slash arguments and reject invalid flags

[AetherAI3]

Fixes #276.

Change

• Preserve the raw slash arguments in the dispatcher and parse quoted values, escapes, and --flag=value without a shell.
• Accept /ship title, body, base, approval, yes, JSON preview, and help options. Reject missing values, unterminated quotes, unsupported or duplicate flags, and positional input with usage before any publication step.
• Update /help ship and generated command documentation.

Evidence

• The actual shipSlash wrapper keeps a Unicode title with quotes and literal $(...)/backticks, and a multiline body, as single argv values matching the CLI parse.
• The JSON preview's gh pr create argv matches the fake GitHub call after approval.
• Malformed inputs trigger zero Git/GitHub calls and zero confirmation prompts.
• Focused checks: build; review/ship/manifest suite (36 passed, 1 platform skip); new slash cases (3 passed); slash and ship rail suite (37 passed); generated docs check; git diff --check.

[AetherAI3]

Final gate review for exact head 37df79b95c1c12657e617d6b8846205419d4a8eb before administrator merge:

• The self-hosted Linux test step passed: 3,029 passed, 11 skipped, 0 failed (3,040 total).
• The self-hosted Windows test step passed: 2,995 passed, 45 skipped, 0 failed (3,040 total).
• Linux and Windows clean-install jobs both passed.
• CodeQL analysis completed successfully (CODEQL_ACTION_ANALYZE_DID_COMPLETE_SUCCESSFULLY: true). Its job was red because the required exact-source artifact upload hit the GitHub Actions storage quota.
• The PyPI launcher checks ran; its job was red for the same artifact quota.
• The Linux and Windows test jobs were red after the passing test steps because the pinned AetherAI3/ATSv2 checkout returned repository-not-found, and the exact-source artifact upload hit quota.
• The supply-chain job passed its package production check; release:truth reported 11/12 checks passing, with the sole failure that the operator packet still says candidate after 0.4.0 was published. Its artifact uploads also hit quota.

These are failures in shared release evidence and repository access, not passing required statuses. The /ship change itself passed its focused wrapper and parity tests and the full Linux/Windows Node suites. The repository's per-PR self-hosted runner opt-in was temporarily set to #293 for this run and restored to #292 after all #293 jobs were assigned. The issue owner explicitly authorized proceeding after these gate details were surfaced, so the merge uses the repository administrator bypass rather than presenting the red checks as green.