Improve agent-oriented CLI workflows

[mamoreau-devolutions]

Summary

• Add stable agent-facing CLI contracts: envelope output, structured error classification/exit codes, CLI schema discovery, MCP structured content/tool annotations, and truncation metadata.
• Add canonical agent debugging workflows: debug capabilities, debug snapshot, riage, symbols doctor, �reakpoint plan, remote doctor/status/plan, and optional action logging.
• Expand docs, discovery metadata, integration tests, and Windows smoke CI coverage for the new agent workflows.

Validation

• cargo fmt --check
• cargo test --workspace
• cargo clippy --workspace --all-targets
• git diff --check
• Local smoke tests for no-daemon agent commands and daemon-backed dump-target agent commands

[awakecoding]

Superseded by #5, opened from the awakecoding-owned branch.