fix(hooks): register dynamically loaded hook modules

[林SO (Linxiushen)]

Fixes #605

Custom rollout hooks containing a dataclass and from __future__ import annotations fail during loading because load_hooks does not register the executing module in sys.modules. Register the module before execution, use a name derived from its resolved path so different hook files do not collide, and restore the previous registration if execution, validation, or construction fails.

The regression tests load real Python files and execute on_enqueue with RolloutCreate. They cover postponed annotations, independent module identities through pickle round trips, and rollback after module execution, class validation, or constructor errors. On the original source these tests produce 6 failures and 2 passes; all 8 pass with the fix.

Validation:

• uv sync --frozen --no-default-groups --extra dev --group dev --group verl-cpu followed by uv run --locked --no-sync pytest -v --durations=20 tests: 128 passed, on Linux/Python 3.12.14 with CPU PyTorch.
• uv run --locked --no-sync pyright: 0 errors, 0 warnings.
• Full repository Ruff lint/format, copyright-header check, and pre-commit hooks pass.
• uv build: source distribution and wheel built successfully.

Developed with Codex assistance and independent agent review. No GPU training was run; this change is confined to the Python hook loader.

[Copilot]

Copilot review overview

🟢 Approval recommended

The focused implementation correctly addresses the loader defect and includes comprehensive regression coverage.

Review effort: Balanced
Findings: None

What changed in this PR

Fixes dynamic hook loading by registering path-unique modules, enabling postponed annotations and pickle support.

Changes:

• Registers hook modules in sys.modules with deterministic path-based names.
• Restores prior module state when loading fails.
• Adds regression coverage for dataclasses, pickling, module isolation, and failures.

File	Description
agentlightning/​hooks.py	Adds collision-resistant module registration and rollback.
tests/​test_hooks.py	Tests successful loading, isolation, pickling, and cleanup.

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