Improve Codebase Evolution views and semantic diffs

[forhappy]

Summary

• render source changes, changed graph, and semantic findings as three focused comparison tabs
• redesign semantic findings as spacious expandable evidence cards with readable field layouts and expand/collapse-all controls
• preserve diffs.com native Shadow DOM subgrids so every source line contributes to the component natural height
• allow the history webview's Diffs-generated grid-span style attributes through a narrow style-src-attr CSP directive
• mirror the installed webview CSP in the browser fixture so development tests catch VSIX-only layout failures
• keep VS Code theme customization on documented host CSS variables instead of structural unsafe CSS
• move update and watch controls onto each repository status row with distinct sync, watch, and stop icons
• replace the Maintain group with a focused settings menu for CLI, repository scope/config, history profiles, and configurable watch behavior
• explain graph-only branch-condition changes using bounded source-hunk evidence and exact function spans
• classify supported logic changes with partial control-flow completeness, without inventing unsupported behavior

Root cause

@pierre/diffs generates per-file grid spans as HTML style attributes. The installed VS Code webview kept those attributes visible in DevTools, but its production CSP blocked them from applying, so grid-row: span N computed to auto and every diff line occupied the same row. The --diffs-min-number-column-width-default: 2ch value only controls gutter width and was unrelated.

The fix permits style attributes only in the Codebase Evolution webview; it does not enable arbitrary inline style elements or relax script policy.

Semantic-diff qualification

• replayed real repository histories from Podman, CocoIndex, and LevelDB
• added focused coverage for condition changes, irrelevant hunks, multiline conditions, and bounded evidence
• documented the graph-only language behavior and its evidence limits

Screenshots

Source changes — dark theme

Changed graph — dark theme

Semantic findings — light theme

Verification

• cargo fmt --all -- --check
• cargo test --workspace
• cargo clippy -p compass-semantic-diff --all-targets --all-features --no-deps -- -D warnings
• 44 Compass viewer tests
• 47 VS Code extension tests
• 13 Codebase Evolution browser tests
• viewer and extension TypeScript checks
• installed the rebuilt VSIX into an isolated VS Code 1.130 profile and verified the real entire comparison
• verified the three installed diff hosts render at natural heights of 340px, 372px, and 61px, with computed grid spans of 16, 17, and 2
• packaged compass-vscode-0.1.1.vsix
• visually verified comparison tabs and diff rendering in dark and light themes
• refreshed the Graphify knowledge graph with graphify update .

Known baseline

Workspace-wide Clippy still reports five pre-existing needless_borrow findings in compass-graph; the touched semantic-diff crate is clean with warnings denied.