Expand TTD and AI debugger workflows

[mamoreau-devolutions]

Summary

• add TTD recording with capture controls, filtering, diagnostics, and CET-compatible target support
• honor standard Windows symbol environment variables across symbol-loading workflows
• add native DbgEng live startup-break support with structured degraded-state diagnostics
• add agent-oriented target event and per-thread context inspection through CLI and MCP

Validation

• cargo fmt --check
• cargo test -p windbg-dbgeng -p windbg-ttd -p windbg-tool
• cargo clippy --workspace --all-targets -- -D warnings
• cargo build -p windbg-tool

cargo test --workspace remains blocked by the existing windbg-install elevation requirement (os error 740).