feat(agent-runtime): add CLI composition flows (Phase 4)

[yacosta738]

Related Issues

Part of #430 (epic), closes #481 (Phase 4: CLI composition flows)

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Summary

Implements Phase 4 of the capability-based architecture: CLI composition flows that let operators build, run, and scaffold agents from TOML manifests.

What changed:

• src/composer.rs — new module with handle_composer_command dispatcher and three handlers:
  • handle_build_command: loads and validates manifest via AgentComposer, checks capability availability against the registered registries, scaffolds output directory
  • handle_run_command: validates manifest + platform constraints (sandbox availability), stubs boot-time run with a clear "not yet implemented" error pointing to build
  • handle_new_command: generates a ready-to-use TOML manifest from three built-in templates (chat-bot, support-bot, code-assistant)
• src/main.rs — Commands::Agent extended with an optional AgentCompositionCommands subcommand (build, run, new); legacy interactive loop is fully preserved when no subcommand is given
• src/lib.rs — added pub mod composer and renamed the re-export from composer to corvus_composer to avoid the name collision

What did NOT change:

• No existing trait signatures modified
• No existing CLI contracts broken — corvus agent without subcommands behaves identically to before
• No corvus-composer crate internals changed

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Tested Information

• cargo clippy --all-targets -- -D warnings → clean
• cargo fmt -- --check → clean
• cargo test --lib → 3493 tests, 0 failures
• 15 new unit tests in composer::tests covering:
  • All three template generators (content assertions)
  • handle_new_command validation: empty name, slash in name, unknown template, file creation
  • handle_build_command: happy path with temp manifest, missing manifest error
  • handle_run_command: "not yet implemented" error, missing manifest error
  • check_sandbox_availability: none always available, unknown sandbox rejected, Linux-only sandboxes unavailable on non-Linux

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Documentation Impact

• No docs update required because this PR adds new CLI subcommands with self-describing --help output; no external APIs or configuration schemas changed.

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Breaking Changes

None. The corvus agent command is fully backward-compatible.

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Checklist

• I have checked that there isn't already a PR solving the same problem.
• I have read the Contributing Guidelines.
• I ensured my code follows the project's style guidelines.
• I have added or updated tests that prove my fix is effective or that my feature works.
• I have updated the documentation, or I explained above why no documentation update is needed.
• I verified the documentation matches the current behavior.
• I have documented any breaking changes in the Breaking Changes section.
• I have linked the related issue (if any).

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[github-actions]

✅ Contributor Report

User: @yacosta738
Status: Passed (12/13 metrics passed)

Metric	Description	Value	Threshold	Status
PR Merge Rate	PRs merged vs closed	89%	>= 30%	✅
Repo Quality	Repos with ≥100 stars	0	>= 0	✅
Positive Reactions	Positive reactions received	10	>= 1	✅
Negative Reactions	Negative reactions received	0	<= 5	✅
Account Age	GitHub account age	3088 days	>= 30 days	✅
Activity Consistency	Regular activity over time	108%	>= 0%	✅
Issue Engagement	Issues with community engagement	0	>= 0	✅
Code Reviews	Code reviews given to others	545	>= 0	✅
Merger Diversity	Unique maintainers who merged PRs	2	>= 0	✅
Repo History Merge Rate	Merge rate in this repo	92%	>= 0%	✅
Repo History Min PRs	Previous PRs in this repo	231	>= 0	✅
Profile Completeness	Profile richness (bio, followers)	90	>= 0	✅
Suspicious Patterns	Spam-like activity detection	1	N/A	❌

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_{Contributor Report evaluates based on public GitHub activity. Analysis period: 2025-04-11 to 2026-04-11}