Add command-oriented CLI and Fish shell completion

[dapi]

Problem

Several independently invokable operations are still expressed as root flags or long legacy command names. The CLI does not expose shell completion, so commands, command-specific options, enum values, prompt names, and relevant paths are not discoverable from Fish.

Routing

• Flow: Feature Flow.
• Rationale: this is one delivery unit that materially changes the public CLI contract and adds a persistent shell-integration operation; it is not eligible for Small Change.
• Planned feature package: memory-bank/features/FT-043/ (link will be added after bootstrap).
• Validation profile: to be selected in the feature brief; minimum expected floor is standard because the public CLI contract changes.

Scope

• Keep code-converge as the primary workflow invocation.
• Add code-converge run as an explicit equivalent.
• Add code-converge review-docs as the command-oriented document-review entrypoint.
• Add code-converge init-prompt as the concise prompt-initialization command.
• Keep and include code-converge config in the command model.
• Keep code-converge update.
• Add Fish completion lifecycle commands:
  • code-converge completion install fish
  • code-converge completion uninstall fish
• Generate completion from one canonical CLI command/option registry shared with help where practical.
• Complete commands, command-specific options, finite enum values, file paths, and project-local review prompt names.
• Update the public README contract and CLI help.

Compatibility

• Do not add version or help commands; retain --version, -h, and --help.
• Preserve the no-command workflow invocation.
• Define and test compatibility behavior for the existing --document-review and init-document-review-prompt forms in the feature design before implementation.
• Ordinary option values such as models, timeouts, and cycle budgets remain options/configuration rather than standalone commands.

Acceptance criteria

• code-converge and code-converge run execute the same workflow with equivalent arguments and exit behavior.
• review-docs, init-prompt, config, and update have command-specific parsing and help.
• Fish completion can be installed and uninstalled idempotently at the correct user completion path without modifying shell profiles.
• Installed completion covers the documented command tree and relevant dynamic/static values.
• Unsupported command/argument combinations fail with actionable usage diagnostics and operational exit code semantics.
• Automated CLI and completion tests pass.
• make docs-lint and the repository test suite pass.