…raction

Add agent model support to the solution generation pipeline:
- Detect -agent suffix models and store problem_dir in GenerationTask
- Add --agent-timeout and --agent-cost-limit CLI arguments
- Branch execute_task to call generate_agent_solution for agent models
- Save .meta.json alongside generated .cpp solutions
- Add import json for metadata serialization

- Copy problem dir to temp directory so agent doesn't pollute originals
- Makes concurrent runs on same problem safe
- Track token usage from streaming message_delta events (only reliable
  source when timeout kills run before ResultMessage arrives)
- Clean up temp dir after extraction

… for agent eval

Build dynamic agent prompts from problem config (time/memory limits,
subtask counts, interactive vs standard). Write test_all.sh and
run_interactive.sh into agent workdir. Embed small sample I/O directly
in prompt. Add CLAUDE.md with solving strategy guidance.

Parity mode (--parity flag) strips all test data, helper scripts, checker,
and interactor from the agent workspace — matching the Harbor adapter setup
where agents must self-test via brute-force cross-validation (对拍).

Changes:
- agent_interface.py: parity-aware prompt, workspace setup, CLAUDE.md,
  _get_infra_git_hash(), and enriched build_metadata (timestamp, parity flag)
- generate_solutions.py: --parity CLI argument
- tests: parity prompt validation (standard + interactive)
- docs: solutions repo separation plan (infra_git_hash in meta.json)
- .gitignore: exclude .claude/ directory
- pyproject.toml: add pytest dev dependency

These belong to the solutions repo separation effort, which is docs-only
for now. Removed _get_infra_git_hash(), subprocess import, and the
infra_git_hash/timestamp/parity fields from build_metadata().

…n doc

Agent always runs without test data — no --parity flag needed.
The solutions repo separation plan is not ready to commit.

Move all large string constants (prompt templates, shell scripts, CLAUDE.md
content) out of agent_interface.py into a dedicated constants module.

…gment room