Complete HookSession input and gradient hook coverage

[Xmaster6y]

Summary

• let HookSession.capture and HookSession.replace target forward inputs, including (args, kwargs) input hooks
• expose both backward gradient-input and gradient-output directions while preserving the existing activation and gradient defaults
• preserve structured input values and record each exact direction and target in the resulting HookProgram
• document the expanded session API and cover success, failure, validation, structure preservation, and cleanup behavior

Validation

• just checks
• just tests — 621 passed, 1 skipped
• uv run pytest tests/test_demo_notebooks.py -q -m integration — 3 passed, 1 deselected
• just docs — passes with the existing AutoAPI cyclic-import warning

Closes #115

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-31T14:22:37.176389Z	cc90792	PR opened

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.31%. Comparing base (1e1b930) to head (9fcbda4).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #129   +/-   ##
=======================================
  Coverage   98.30%   98.31%           
=======================================
  Files          52       52           
  Lines        3947     3968   +21     
=======================================
+ Hits         3880     3901   +21     
  Misses         67       67           

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[cubic-dev-ai]

All reported issues were addressed across 3 files

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