Shape reading mode: fold function bodies in the whole-file view

[davegaeddert]

Spike of the reading-modes arc's first future (futures: review/reading-modes/shape-view.md): a "Shape" toggle for the whole-file view that folds every function/method body to a faint ⋯ marker — signatures, docstrings, fields, and imports stay literal — with per-fold expand/collapse and real line numbers preserved.

Approach

Deliberately without forking @pierre/diffs (which has no fold/hidden-range API and recycles rows while virtualizing): shape mode synthesizes a smaller real document — collapsed bodies removed, one indent-matched ⋯ marker line each — so pierre's virtualization stays correct. Pierre's line numbers are disabled (disableLineNumbers) and a custom self-virtualized gutter (ShapeGutter) renders real line numbers + fold chevrons; on scroll it translates one wrapper instead of rebuilding rows. A collapsed fold's marker occupies the same row its first body line takes when expanded, so single toggles never shift content above the click point. Read-only by design: token/selection/annotation interactions are inert in shape mode, and line-addressed features that speak real-file coordinates (in-file search, go-to-line, outline active-tracking/clicks) are explicitly suppressed while shape is on rather than silently mis-mapped.

Backing data: Symbol gains optional bodyStartLine (1-based first interior line; the signature including its trailing { line stays visible), populated at all 66 construction sites in the tree-sitter extractor. None for one-liners, expression-bodied functions, and bodyless declarations.

Shape state and derivation live in hooks/useShapeMode.ts (component state by design, like svgViewMode/markdownViewMode — promoting to a slice is required only if this ever becomes a palette command). A /simplify four-angle cleanup pass (2a15ea9) shrank the model to the two fields the renderer consumes, hoisted per-toggle hashing/splitting to once per file, and reused ToggleButtonGroup for the fold controls.

Status

• bodyStartLine in core/src/symbols/ (+3 extractor tests: Rust incl. multi-line signatures, Python incl. docstring-as-interior, TypeScript incl. arrow consts)
• Synthesized-document fold view + custom gutter (shape-model.ts pure + 16 unit tests, ShapeGutter.tsx, useShapeMode.ts, toolbar toggle + expand/collapse-all, gated to plain whole-file mode)
• Frontend validation: tsc clean, 628 vitest tests pass
• Visual verification in a browser harness against core/src/symbols/extractor.rs (3.5k lines → 598 rows / 97 folds), re-verified after the cleanup pass: fold markers, multi-line signatures intact, gutter alignment deep mid-file, in-place expand with no scroll shift, expand-all/collapse-all, raw toggle
• Needs a local run: this cloud environment's network policy blocks static.crates.io, so cargo check/cargo test could not run here (Rust code is rustfmt-parse-clean and structurally audited, but the 3 new extractor tests are unrun). Please run scripts/test locally, then scripts/dev-web → open a repo → an unchanged file in whole-file view → the Shape toggle in the toolbar.

Known follow-ups (deliberate spike scope)

• Real-line remapping: search/go-to-line/outline are suppressed in shape mode; buildShapeDocument's rows can carry a real↔doc mapping when someone closes this properly (the suppression site documents the path).
• Deferred Rust refactors from the cleanup review (need a compiler): a Symbol::from_node constructor to collapse the 66 mechanical field initializations; passing precomputed line bounds into body_interior_start; replacing its starts_with('{') text test with the tree-sitter-structural body.named_child(0) answer.
• Outline rows still look clickable in shape mode though clicks are inert; marker rows are syntax-highlighted as plain text.

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