fix(ui): enforce simplified native status row

[matthias-scale]

Context

Follow-up to #2, which was externally squash-merged at the pre-contract head while final validation was still running. This PR applies the captain-approved final UI contract and the gate fixes discovered by the final no-mistakes run. It does not merge or revert #2.

Source provenance remains RaviTharuma at af5ac9d9b1f6425be600cbb904fda905ea882eb9 from upstream PR herdrdev#1742.

Acceptance criteria

• The native row remains one full-width row above the sidebar/tab surface without changing content-row or mouse geometry.
• The left side is blank. The only visible right-side fields are folder -> branch -> device -> Herdr build version -> CPU -> memory, in that order.
• Username, network/API trace, download/upload, battery, date/time, and session/workspace/tab/pane identity are neither rendered nor reintroduced.
• CPU and memory retain stable labels and units, explicit unavailable fallbacks, fixed display widths, bounded nonblocking refresh, and local native/proc sources only.
• Narrow layouts elide folder, branch, then device while preserving build version, CPU, memory, and at least one blank leading cell at the desktop boundary.
• Headless sampling waits until a renderable status geometry has produced a frame; resize and detached-server paths do not collect unseen metrics.
• Fork contributor checks complete successfully without resolving the canonical-only token action.
• Separate-git-dir and linked-worktree repository naming use deterministic Git metadata/config precedence.

Verification

• just ci test(/status/): 138 passed.
• just check: 3,007 Rust tests passed; integration assets and plugin marketplace passed; Windows MSVC cross-clippy passed; 94 maintenance tests passed.
• Independent gpt-5.6-sol review: PASS after fixed-width metric, resize-order, and blank-boundary fixes; zero P0/P1.
• no-mistakes run 01KYS8PMVJW67GSKC7Y4CE1QGP: PASS at the tree replayed by this head; review/test/document/lint complete. Push/PR/CI were deliberately handled manually to prevent another wrong-base PR.
• Renderer evidence covers wide, 120-column, and unavailable-metric frames.

Pending exact-head gates

• Linux/macOS/Windows GitHub checks at this exact head.
• Disposable combined validation with focused-sidebar PR feat(ui): focus the sidebar around a spaces tree with per-workspace agent disclosure #1 head 9dc635c0043ba5e695e95c02fcd580fe80d3dc43 and the per-window active-duration/last-active-age work.

No merge is authorized.

[matthias-scale]

superseded: native status row replaced by turn-end status contract (PR #39); closing per consolidation survey