tui: migrate remaining layouts to Grid

[Michael Greene (mgreenegit)]

Review boundary

Final slice: migrate callers and remove the table API. Review/merge order: #950 -> #961 -> #962.

Review only this slice: 192 additions / 123 deletions across six files (315 changed lines, down from 329). The comparison uses a content-identical linear review snapshot; this PR retains one cumulative commit against main, including both unmerged prerequisites.

Changes

• Migrate all 11 table-construction sites: search/replace, action groups, file-picker forms, statusbar/indentation/encoding controls, menubar, and flyouts.
• Use declarative shared rows, intrinsic sizing, gaps, and navigation while preserving focus hierarchy, row identity, floats, and hitboxes. Omit 14 redundant settings where defaults suffice.
• Use fractional fill columns in constrained search/file-picker forms; retain unrelated sizing sentinels.
• Delete the table API. Shared layout algorithms and generic Grid tests are unchanged from tui: unify layout through boxed Grid subgrids #961.
• Extend the existing application scenario for dialog Tab/ShiftTab/arrow navigation and file-picker alignment, typing, cancellation, and restored editor focus.

This pull request was drafted by a large language model (LLM).

Validation

• Latest local validation: nine Grid tests and two application layout tests pass, along with formatting, pre-commit workspace Clippy, and scoped structural checks.
• The TUI-only optimization is carried forward unchanged from tui: unify layout through boxed Grid subgrids #961; this slice's incremental scope and all tests are unchanged.
• Source comparisons confirm unchanged shared algorithms/tests and no remaining table API calls or content variants.
• Final-head Windows/Ubuntu CI and CodeQL pass at c33ecee.

This completes the existing table migration, not full CSS support. No Flexbox, arbitrary spans, stylesheet parser, console/provider/AI work, or new dependencies.