refactor(desktop): retire dead Task Ledger CSS and align it with SessionTodoPanel

[liuxiaocs7]

Summary

#4351 replaced the nested Task Ledger demand chain with the Host-owned, flat SessionTodo document (SessionTodoPanel), but apps/desktop/src/renderer/styles/task-ledger.css still described the retired four-column, depth-indented tree row.

Beyond selectors that could no longer match any element, the row padding fed a calc() referencing the never-defined --task-depth, which makes the whole padding declaration invalid at computed-value time — so on main these rows actually render with padding: 0. This reduces the sheet to what the flat <li> renders and renames it to match the component:

• The row is now a two-column [icon] [text] grid whose content wraps within the panel width — dropping the 4-column grid-template-columns (which reserved a phantom ≥100px empty column) and the --task-depth indent. Removing the invalid calc() restores the intended var(--space-1) var(--space-2) padding the rows were meant to have.
• Removed dead rules: -group, the [data-status] icon-color rules (data-status is never set; SessionTodoStatus is only pending/in_progress/completed, distinguished by glyph), -key/-subject/-meta/-detail, -terminal/-terminal-trigger (no such elements exist), and the row :focus-visible (the <li> is not focusable).
• Deleted the @media (max-width: 620px) block rather than porting it: the flat row wraps at any width. A comment records that future width-responsive styling should be an @container query on the panel (matching workbar/inspector.css / chat-header.css), because the workbar shrinks to SESSION_WORKBAR_MIN_WIDTH (320px) inside a wide window where a viewport @media never fires — the @container approach from fix(desktop): contain deeply nested task rows in the task panel #4215.
• Renamed styles/task-ledger.css → styles/session-todo-panel.css and the maka-task-ledger-* class prefix → maka-session-todo-*; updated the @import, the historical maka-tokens.css reference, and regenerated the Astryx surface inventory.

The packages/storage task-ledger-authority.test.ts tmpdir string is a separate storage-layer concept and is intentionally untouched.

Fixes #4394

Behavioral change

On main the row padding is invalid at computed-value time (undefined --task-depth), so task rows render flush with padding: 0. Removing the dead --task-depth restores the intended var(--space-1) var(--space-2) inset, and the row drops from a 4-column grid (with a phantom ≥100px column) to auto minmax(0, 1fr). Net effect: task-list rows regain their horizontal inset and vertical spacing, and long content now wraps within the panel instead of relying on the old auto-sized column.

Rendered headlessly from the real stylesheets — main's task-ledger.css vs this PR's session-todo-panel.css — over the actual maka-tokens.css and the panel's real markup, so it shows the true computed-layout delta rather than a mock (the status glyph is a stand-in). The same rows render in situ in the Product/Session Workbar → Tasks story.

Verification

• npm run astryx:surface-inventory — passes (231 files); regenerated docs/astryx-surface-file-inventory.{md,paths} match generator output.
• node scripts/asf-license-headers.mjs check — passes.
• biome lint on all changed source files — 0 violations.
• Repo-wide grep: no remaining maka-task-ledger-* usage (outside the unrelated storage test) and no dangling task-ledger.css reference.
• Renderer-architecture snapshot is not affected (its generator scans only .ts/.tsx; no renderer .tsx changed).
• The visual states already have a real-host surface — Product/Session Workbar → Tasks / TasksEmpty / TasksLoadFailed (apps/desktop/stories/session-workbar.stories.tsx) render SessionTodoPanel through the workbar's real todo.read service. The populated Tasks story is where the restored row padding (0 → var(--space-1) var(--space-2)) is visible, with no code change needed there. (An earlier standalone Product/Session Todo story was removed on review: it used a hand-rolled frame and duplicated these states, which apps/desktop/stories/FIDELITY.md disallows.)
• Before/after screenshot: included in Behavioral change above — rendered headlessly (Playwright + the desktop's Chromium) from the real maka-tokens.css and both stylesheet versions, so it shows the actual computed-layout delta rather than a mock. It is not a full-app capture; the real-host Product/Session Workbar → Tasks story shows the same rows in situ.
• Not run here (no installed workspace deps): full desktop build/typecheck and the @maka/ui unit test. The @maka/ui change is a className string literal that cannot affect types, and session-todo-panel.test.tsx asserts only text ordering, not classes.

Review focus

The one visible change is the restored row padding (rows render at padding: 0 on main). It shows in the existing Product/Session Workbar → Tasks story with no story change needed. Please compare that story — or the running app — on main vs this branch; before/after screenshots still need attaching from a GUI host.

AI use

• Generative tooling made a substantive contribution

Tool(s) and scope: Authored with Claude Code — analysis of the retired contract (including the invalid --task-depth padding), the CSS reduction and rename, inventory regeneration, and this description. The commit carries a Generated-by: Claude Code trailer.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Behavioral change above
• No