feat: add terminal-shell engineer foundation

[rysweet]

Summary

• add a real terminal-shell engineer base type backed by a local PTY shell session
• surface truthful terminal capability/topology metadata in runtime reflection and the operator probe
• add operator-style outside-in coverage plus doc/spec reconciliation for the shipped v1 slice

Why

The original Simard prompt and Specs/ProductArchitecture.md both require an engineer path that executes repository tasks through terminal actions rather than only a synthetic local harness. This PR lands an honest local-first foundation without pretending to support remote or distributed terminal orchestration yet.

Shipped scope

• new builtin engineer base type: terminal-shell
• backend identity: terminal-shell::local-pty
• topology support: single-process only
• PTY-backed command execution and transcript evidence via simard_operator_probe terminal-run
• reflection fields for adapter capabilities and supported topologies

Explicit non-goals in this PR

• remote hosts or Azlin orchestration
• distributed terminal control
• full interactive multi-turn operator UI
• a distinct real copilot-sdk backend

Validation

• cargo fmt --all
• cargo test --all-features --locked
• tests/gadugi/smoke-explicit-local.sh
• tests/gadugi/smoke-explicit-rusty-clawd.sh
• tests/gadugi/smoke-builtin-defaults.sh
• tests/gadugi/composite-identity.sh
• tests/gadugi/meeting-mode.sh
• tests/gadugi/terminal-session.sh
• tests/gadugi/handoff-roundtrip.sh
• tests/gadugi/review-mode.sh
• tests/gadugi/gym-suite.sh
• python3 -m pre_commit run --all-files --hook-stage pre-commit
• python3 -m pre_commit run --all-files --hook-stage pre-push

Closes #36.