feat(sidebar): daily-notes panel + Q&A deep-link to file offset

Daily notes panel:
- src/sidebar/daily-notes-panel.js — new sidebar panel that lists every
  YYYY-MM-DD.md in the daily-notes dir (newest first), with a Today
  button that creates/opens today's entry. Refresh button reloads.
  Clicking a row calls onOpenFile(path). DOM is built with textContent
  for dynamic fields — no XSS surface from a hostile filename.
- src/main.js — daily-notes:list IPC now returns absolute paths (joined
  with the daily-notes dir) so the renderer can pass them straight to
  open-file-path without re-synthesizing.
- src/renderer.js — registers the panel; icon for the daily-notes
  button (calendar icon).
- src/index.html — calendar SVG icon for the daily-notes sidebar entry.

Q&A deep-link:
- src/main.js — open-file-path accepts either a string (legacy) or an
  object {path, offset}. The offset is forwarded to the renderer via
  file-opened.
- src/renderer.js — file-opened handler scrolls the editor to the
  offset using EditorView.scrollIntoView(y: 'center') so the matching
  passage lands in the middle of the visible area.
- search panel now passes {path, offset} to open-file-path so Q&A
  results with chunk offsets jump straight to the passage.

Tests (12 new, tests/daily-notes-panel.test.js):
  - mount, empty state, list rendering
  - Today button → onOpenFile, 'Created today' / 'Today already exists' status
  - error paths (openToday reject, listExisting reject, listExisting missing)
  - click + Enter/Space on a row open the right path
  - refresh() re-fetches, keeps status when keepStatus:true
  - non-md entries filtered out
  - XSS-safe textContent for dynamic data

Full suite: 73 suites, 873 tests, lint+format clean.

Amit Haridas

src/index.html

@@ -2574,6 +2574,24 @@
                 <line x1="21" y1="21" x2="16.65" y2="16.65" />
               </svg>
             </button>
+            <!-- Daily notes: list of YYYY-MM-DD.md files + Today button -->
+            <button class="sidebar-icon" data-panel="daily-notes" title="Daily Notes (Ctrl+Alt+D)">
+              <svg
+                width="20"
+                height="20"
+                viewBox="0 0 24 24"
+                fill="none"
+                stroke="currentColor"
+                stroke-width="2"
+                stroke-linecap="round"
+                stroke-linejoin="round"
+              >
+                <rect x="3" y="4" width="18" height="18" rx="2" />
+                <line x1="16" y1="2" x2="16" y2="6" />
+                <line x1="8" y1="2" x2="8" y2="6" />
+                <line x1="3" y1="10" x2="21" y2="10" />
+              </svg>
+            </button>
           </div>
           <div class="sidebar-panel" id="sidebar-panel">
             <div class="sidebar-panel-header">