fix(call): default Accept to AcceptTrusted + add log Copy/Share buttons

## Accept button regression — diagnosed from a user log

Field report: incoming call → callee taps Accept → debug log
shows the dual-path race being skipped with
`connect:dual_path_skipped {"has_own":false,"has_peer":true,
"role":"None"}` and the call falling to relay-only on the
callee side.

Root cause: the Accept button was calling `answer_call` with
`mode: 2` which falls through to `AcceptGeneric` (privacy
mode). By design, privacy mode SKIPS the reflex query on the
callee so the callee's IP stays hidden from the caller — but
the side effect is that `own_reflex_addr` never gets cached in
`SignalState`. When `connect` runs a moment later, it sees
`own_reflex_addr = None`, can't compute the deterministic role
for the dual-path race, and falls back to relay.

For a normal VoIP app where P2P is the desired default, the
right behavior is `AcceptTrusted` — which queries reflect,
advertises the callee's addr in the answer, and enables direct
P2P. Privacy mode can come back as a dedicated second button
if anyone actually needs it.

Changed `acceptCallBtn` click handler from `mode: 2` to
`mode: 1`. The next call from a Phase-5 APK should show
`connect:dual_path_race_start` + `connect:dual_path_race_won
{"path":"Direct"}` on a cone-NAT-to-cone-NAT pair.

## Debug log export — new Copy / Share buttons

Field-testing the GUI debug log required me to keep asking the
user to type out what they saw. Added two new buttons next to
Clear:

- **Copy log** — serialises the rolling buffer as plain text
  (same HH:MM:SS.mmm format the on-screen panel uses) and
  writes to `navigator.clipboard`. Falls back to the old
  selection-based `execCommand("copy")` for WebViews that
  refuse the new API without a permission prompt.

- **Share** — tries the Web Share API (`navigator.share(...)`)
  first. On Android WebView this opens the system share sheet
  so the user can send the text straight to a messaging app.
  Falls back to clipboard copy on WebViews that don't expose
  navigator.share (most desktop ones). Also falls back if the
  user cancels the share sheet.

Flash status line below the buttons shows a 2.5s confirmation
("✓ Copied 47 entries") or an error hint. The log is plain
text so anyone can paste a log fragment into a message and
send it.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktop/index.html

@@ -181,7 +181,12 @@
           <div class="settings-section" id="s-call-debug-section" style="display:none">
             <h3>Call Debug Log</h3>
             <div id="s-call-debug-log" style="max-height:220px;overflow-y:auto;background:#0a0a0a;color:#e0e0e0;font-family:ui-monospace,Menlo,Monaco,'Courier New',monospace;font-size:10px;padding:6px;border-radius:4px;line-height:1.4;white-space:pre-wrap"></div>
-            <button id="s-call-debug-clear" class="secondary-btn" style="margin-top:6px">Clear log</button>
+            <div style="display:flex;gap:6px;margin-top:6px">
+              <button id="s-call-debug-copy" class="secondary-btn" style="flex:1">Copy log</button>
+              <button id="s-call-debug-share" class="secondary-btn" style="flex:1">Share</button>
+              <button id="s-call-debug-clear" class="secondary-btn" style="flex:1">Clear log</button>
+            </div>
+            <small id="s-call-debug-copy-status" style="display:block;margin-top:4px;color:var(--text-dim);font-size:10px"></small>
             <small style="color:var(--text-dim);display:block;margin-top:4px">
               Rolling buffer of the last 200 call-flow events. Turned off by
               default — the GUI overlay only populates when the checkbox above