[AetherAI3]

Closes #320.

Change

• Add --prompt-file <path|-> to aether agent and its code alias. Read one bounded UTF-8 source to EOF and pass its literal text to the existing coding task path.
• Reject positional tasks, resume, interactive steering, managed-agent routing, and --with-token before reading stdin or starting a session.
• Record source and byte count in diagnostics and session metadata while using a generic run label instead of logging the prompt body.
• Document the 256 KiB cap, conflict table, file and pipe examples, and generated command help.

Evidence

• npm run build passed.
• node --test --test-isolation=none dist/test/prompt_file.test.js dist/test/brain_cloud_dev.test.js dist/test/brain_ollama.test.js dist/test/code_verification_path.test.js dist/test/command_manifest.test.js dist/test/command_registry.test.js dist/test/command_dispatch.test.js dist/test/command_docs_parity.test.js: 86 passed, 0 failed.
• npm run docs:check passed.
• git diff --check passed.