feat: add session log search

[abachman]

Summary

• add less-style inline search for the session log pane
• highlight all matches and navigate results with up/down
• add UI tests for search matching, navigation, resize, and clear behavior

Testing

• make test

[github-actions]

Merging this branch will not change overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/reasonable-systems/ccsessions/internal/ui	0.00% (ø)

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Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/reasonable-systems/ccsessions/internal/ui/model.go	0.00% (ø)	0	0	0

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/reasonable-systems/ccsessions/internal/ui/model_test.go