Files pane: wire up git change indicators for file icons

[pedramamini]

Context

The Session.changedFiles field (FileArtifact[]) exists on the session interface but is never populated with actual git status data. It's initialized as [] in every session creation path (useSessionCrud.ts, useWizardHandlers.ts, worktreeSession.ts, tabHelpers.ts) and no code ever writes to it.

The file explorer already has plumbing to consume this data:

• FileExplorerPanel.tsx:941 — const change = session.changedFiles?.find((f) => f.path.includes(node.name));
• FileExplorerPanel.tsx:1021 — passes change?.type to getExplorerFileIcon()
• Default theme has fileTypeColor() that maps added→green, modified→yellow, deleted→red

But since changedFiles is always empty, none of this has any visible effect.

Additionally, PR #609 (Files Pane Icon Theme) adds a "Rich" icon theme that accepts but ignores the _type parameter entirely in getRichExplorerFileIcon(). Once changedFiles is wired up, the rich theme will need to handle diff status too (e.g., colored dot overlay, border, or CSS filter on the <img> SVG icons).

What needs to happen

1. Populate changedFiles — Run git status (or equivalent) and write results into session.changedFiles with proper FileArtifact.type values (added, modified, deleted). This should refresh on file tree refresh and after agent operations complete.

2. Default theme — Already wired via fileTypeColor(). Should work once data flows. Verify visually.

3. Rich theme — getRichExplorerFileIcon currently discards _type. Add a visual indicator for change status — options include:

   • Colored dot/badge overlay on the icon
   • CSS filter or opacity shift
   • Colored left border on the file row

   Whatever approach is chosen, it should be consistent with how the default theme communicates the same information.

4. File name match — The current lookup (f.path.includes(node.name)) is fragile and could false-match (e.g., a file named utils.ts matching src/other/utils.ts). Consider matching against the full relative path instead.

Relevant files

• src/renderer/types/index.ts:531 — changedFiles: FileArtifact[] definition
• src/renderer/components/FileExplorerPanel.tsx:941 — consumption site
• src/renderer/utils/fileExplorerIcons/richTheme.tsx — getRichExplorerFileIcon (ignores _type)
• src/renderer/utils/fileExplorerIcons/defaultTheme.tsx — getDefaultExplorerFileIcon (has fileTypeColor)
• src/renderer/utils/fileExplorerIcons/shared.ts — shared types including FileChangeType

[jeffscottward]

Note: for clarity

In VS Code it highlights the file names and folders matching against the full relative path, and an circle indicator, for modified and newly added files, walking the tree to highlight its location. We DO NOT want to override/modify the icons themselves so that those may stay consistent regardless of the color theme (default icon set) or state of the file.

Instructions to AI: Please evalute how VSCode does it either with the images included here or from the VSCode code base from Microsoft.