emrg: fix GUI sidebar layout — pin status dot to bottom, remove duplicate divider

[argszero]

Fixes the GUI left sidebar layout (rant 2026-08-22T07:10:44).

Changes (emrg/gui/renderer/css/layout.css)

1. Status dot not pinned to the bottom: #sidebar is a flex-direction: column container but had no full height, and .sidebar-footer (which holds the status-dot) had no margin-top: auto, so the green dot floated below the session list instead of sitting against the sidebar's bottom edge.

   • #sidebar: added height: 100% so the column flex fills #app's 100vh.
   • .sidebar-footer: added margin-top: auto — in a column flex this pushes the footer to the container's bottom edge.

2. Duplicate divider line: #open-sessions had a border-bottom and .sidebar-footer a border-top, sitting right next to each other (only margin-bottom: var(--sp-1) between them) — visually two parallel lines.

   • Removed #open-sessions's border-bottom; .sidebar-footer's border-top remains as the single divider.

Verification

• uv run pytest tests/: 1002 passed, 1 skipped
• python -c "from emrg.client.app import run_client": OK
• python -m emrg --help: OK

CSS-only change; no test count change.

[argszero]

✅ LGTM — cycle 1244. Verified the CSS diff (layout.css, +2/−1): #sidebar height:100% pins the footer, .sidebar-footer margin-top:auto anchors the status dot to the bottom edge, #open-sessions border-bottom removed leaving a single divider. CI green (test + test-windows run 32536412551).

[argszero]

✅ LGTM — cycle 1245. Re-verified: head 71a8e6c mergeable, CI test+test-windows green (run 32536412551). CSS-only change is correct.

[argszero]

✅ LGTM — cycle 1246. Fresh re-verify: head 71a8e6c mergeable, CI test+test-windows green (run 32536412551), CSS-only diff correct.