fix(#1204): MESH LIVE panel — header inherited column flex from .live-overlay (#1215)

Red commit: c159a1153d (CI run: pending —
first CI is on this PR)

Fixes #1204.

## Root cause

`.live-overlay` (the base class for all overlay panels: feed, legend,
node-detail, header) declares `flex-direction: column`. Feed/legend/
node-detail need that for their `.panel-header` + scrollable
`.panel-content` stacking — but the header doesn't, it's a horizontal
bar.

PR #1180 (#16c48e73) split the header from a flat layout into three
children: `.live-header-critical` (beacon + `0 pkts`) + collapsible
toggle button + `.live-header-body` (title + stats row). Without an
explicit `flex-direction` override, those three pieces inherited the
column default and stacked vertically — pushing `0 pkts` above the
`MESH LIVE` title and clipping the stats row out of the 40px max-height
container. Exactly the "detached counter, hollow shell" the issue
reports.

## Fix

Add `flex-direction: row` to `.live-header` (one line + comment).
Single-property CSS change, no JS, no DOM, no behavior outside layout.

## TDD

Red commit `c159a115` — E2E
`test-issue-1204-live-panel-structure-e2e.js`
asserts:
1. `.live-header-critical` and `.live-title` vertically overlap (same
row).
2. `#livePktCount` pill and title mid-Y differ by < 8px.
3. `.live-stats-row` is visible (nonzero size).
4. `.live-feed .panel-content` accepts an injected row (column
container).

Verified failing on master at red commit (3 of 5 fail with the exact
"stacked above title" signature). Green commit `b7f57072` flips all to
pass.

E2E assertion added: `test-issue-1204-live-panel-structure-e2e.js:55`

## Verified

- Local `cmd/server` + fresh fixture, viewport 1440×900, headless
Chromium: 5/5 pass.
- Preflight (`run-all.sh origin/master`): clean.

## Files

- `public/live.css` — `flex-direction: row` on `.live-header` (+
rationale comment)
- `test-issue-1204-live-panel-structure-e2e.js` — new E2E (added to
`deploy.yml`)

---------

Co-authored-by: corescope-bot <bot@corescope.local>

.github/workflows/deploy.yml

@@ -253,6 +253,7 @@ jobs:
           CHROMIUM_REQUIRE=1 BASE_URL=http://localhost:13581 node test-issue-1109-hamburger-dropdown-visible-e2e.js 2>&1 | tee -a e2e-output.txt
           CHROMIUM_REQUIRE=1 BASE_URL=http://localhost:13581 node test-live-layout-1178-1179-e2e.js 2>&1 | tee -a e2e-output.txt
           CHROMIUM_REQUIRE=1 BASE_URL=http://localhost:13581 node test-live-mql-leak-1180-e2e.js 2>&1 | tee -a e2e-output.txt
+          CHROMIUM_REQUIRE=1 BASE_URL=http://localhost:13581 node test-issue-1204-live-panel-structure-e2e.js 2>&1 | tee -a e2e-output.txt
           CHROMIUM_REQUIRE=1 BASE_URL=http://localhost:13581 node test-nav-drawer-1064-e2e.js 2>&1 | tee -a e2e-output.txt
 
       - name: Collect frontend coverage (parallel)