refactor(dashboard): drop FL0W/L0GS/M4TR1X page-links from the tab strip (#1464)

Follow-up to the route swap (#1501): now that every separate page is
reachable from the H0M3 hub, the dashboard tab strip should hold only
real in-page tabs, not the "→" links out to other pages (mara: "remove
links to the pages from dashboard - only actual tabs stay here").

- dashboard.html: remove the `tab-matrix`, `tab-flow`, and `tab-logs`
  `.tab-link` entries (and the stale `tab-count-flow` pill slot — the
  operator inbox moved to Y3R C4LL). The dashboard strip is now SW4RM /
  Y3R C4LL / SYST3M / P3RM1SS10NS / SCH3DUL3S / P33RS / ST4TS / S3TT1NGS.
- tabs.js: drop the now-dead `tab-matrix` matrix_gui_enabled gate (the
  H0M3 Matrix tile is gated by home.js instead) and the obsolete
  `#tab-count-flow` comment. Kept the contextual deep-links into the log
  viewer (an agent's logs, a build entry's log) — those are functional
  content links, not navigation chrome.
- flow.css: remove the dead `.dashboard-chrome.flow-chrome` +
  `.tabbar .tab.active.tab-link` rules — the flow page uses a slim
  back-link header, not the dashboard tabbar, and `.tab-link` no longer
  exists anywhere.

npm run build green (flow.css 1.8kb). No residual references.

frontend/packages/dashboard/src/dashboard.html

@@ -81,40 +81,15 @@
         <span class="tab-count" id="tab-count-peers" hidden></span>
       </a>
 
-      <!-- M4TR1X: optional matrix web client (fluffychat-web by
-           default) mounted at /matrix/ by the gateway when
-           `hyperhive.matrix.gui.enable = true`. Same-origin
-           navigation (the static dist is its own SPA). Hidden in
-           JS when `state.matrix_gui_enabled === false` so operators
-           without matrix-gui on don't see a dead link. See
-           docs/web-ui.md::Tab strip for the gating model and
-           docs/gateway.md for the matrix vhost + .well-known
-           auto-discovery. -->
-      <a class="tab tab-link" id="tab-matrix" href="/matrix/" hidden
-         title="open the matrix chat client (fluffychat-web)">
-        <span class="tab-label">◆ M4TR1X ◆ →</span>
-      </a>
+      <!-- FL0W, L0GS, and M4TR1X are separate pages reachable from the
+           H0M3 hub (served at /), not from the dashboard tab strip — the
+           strip holds only real in-page tabs now. Contextual deep-links
+           into the log viewer (an agent's logs, a build entry's log)
+           still live inside the relevant dashboard content. -->
 
-      <!-- FL0W is its own page (`/flow.html`), not a tab. The link
-           lives in the tab strip so it reads as a peer surface;
-           clicking navigates rather than swapping panes in place.
-           Count pill mirrors the dashboard's operator-inbox length
-           and is hidden when zero. See docs/web-ui.md::FL0W page. -->
-      <a class="tab tab-link" id="tab-flow" href="/flow.html"
-         title="open the all-agents chat in a dedicated full-page terminal">
-        <span class="tab-label">◆ FL0W ◆ →</span>
-        <span class="tab-count" id="tab-count-flow" hidden></span>
-      </a>
-
-      <!-- L0GS and S3TT1NGS: default-overflow — always live in the ⋮
-           dropdown, never in the main strip. `data-overflow="default"`
-           marks them so JS keeps them out of the bar regardless of
-           available width. -->
-      <a class="tab tab-link" id="tab-logs" href="/logs.html"
-         data-overflow="default"
-         title="open the log viewer">
-        <span class="tab-label">◆ L0GS ◆ →</span>
-      </a>
+      <!-- S3TT1NGS: default-overflow — always lives in the ⋮ dropdown,
+           never in the main strip. `data-overflow="default"` marks it so
+           JS keeps it out of the bar regardless of available width. -->
       <a class="tab" id="tab-settings" href="#settings" role="tab"
          aria-controls="tab-pane-settings"
          data-tab="settings"