[Task] Collapse file-type icon sprite into category line-icons

[Astro-Han]

Goal

Replace the upstream vscode-icons multi-color real-brand-logo sprite (~1075 entries in packages/ui/src/components/file-icons/sprite.svg) with ~20–30 generic line-icons grouped by file category, so that file-type icons share the chrome icon DNA (line geometry, single currentColor, 1.5px @ 16 stroke equivalent) instead of staying a visually disjoint multi-color set.

Scope

In scope:

• Define the category set (Code / Markup / Image / Document / Archive / Config / Script / Lock / Data / Binary / Font, ~10–12 buckets).
• Draw ~20–30 line glyphs covering the buckets and the few exceptions that warrant a dedicated glyph (e.g. SVG, PDF, ZIP).
• Replace the existing sprite consumption sites with the new category resolver (filename / extension → category → glyph).
• Update packages/ui/src/components/icon.tsx and any file-icon callsites to use the chrome icon registry path.

Out of scope:

• Redrawing 1075 logos one-for-one.
• App icons under packages/ui/src/assets/icons/app/ (vendor-accurate brand logos, sanctioned exception to the one-icon-DNA rule per DESIGN.md → Iconography → App icons).
• Multi-color treatments for any file type.

Relevant files or context

• packages/ui/src/components/file-icons/sprite.svg (current ~1075-entry upstream sprite)
• packages/ui/src/components/icon.tsx (chrome icon registry)
• DESIGN.md → Iconography → File-type icons (drives the redesign rule)
• DESIGN.md → Do's and Don'ts (one icon DNA across the app)

Verification

• Visual sweep: all file-type icons in the right panel review tab, attachment chips, and any markdown file references render with the same stroke / color / weight as chrome icons.
• Category resolver covers the long tail without falling back to a generic file glyph for common types (.ts, .tsx, .py, .go, .rs, .md, .json, .svg, .png, .pdf, .zip, .lock, etc.).
• Build size: the new sprite is meaningfully smaller than the 1075-entry upstream one.
• No callsite still imports the upstream multi-color sprite.

Execution mode

Agent should investigate and propose a plan first