fix(waitlist): queue + retry failed signups instead of silently opening mailto (#165)

A signup that hit a network error, the 8s timeout or a 5xx was handed straight
to a `mailto:` composer. That path is lossy by design: it only works if the user
actually presses send, and if we keep reconciling the support inbox into Brevo
list 4 forever (AGE-61's hourly job). 20 of 21 signups were lost that way before
that reconciler existed, and Play's active base is ~100% on v0.4.10+ — so this
was current builds leaking, not just the ~436 stale sideloads.

Now:
- Failed-but-retryable signups are persisted on-device
  (`opencode.waitlist.pending.v1`, AsyncStorage) and retried on every app
  foreground (`app/_layout.tsx`) and on the Add Connection screen mount.
- 4xx stays non-retryable: the server will never accept that address, so we ask
  the user to fix it instead of queueing garbage forever.
- `mailto:` is now only ever opened by an explicit user tap ("Still not working?
  Email us instead"), shown after 3 failed attempts, or offered in an alert when
  device storage itself refuses the write — never as the silent default.
- The UI tells the truth: "Saved on this device — we'll finish signing you up as
  soon as you're back online" instead of implying it was sent.
- `WaitlistResult.fallback` -> `retryable`, `shouldFallbackToMailto` ->
  `isRetryableFailure`: the decision is about retry, not about mail.

Queue policy: dedupe by email, cap 5 entries, 30-day TTL, corrupt/foreign JSON
is discarded rather than replayed. Storage and the clock are injected so the
whole thing runs under `node --test` (16 new tests, incl. the acceptance case:
offline signup -> queued -> reconnect -> reaches the server, no mail client).

Also commits the AGE-61 measurement artifacts that were only ever local
(`distribution/waitlist-signup-path-coverage.md`, `scripts/play-version-share.mjs`)
and updates the doc's "current builds still leak" section, which this fixes.

Refs AGE-87, AGE-61.

Co-authored-by: engineer <engineer@macbookpro.lan>

src/lib/i18n/zh-Hans.json

@@ -181,7 +181,11 @@
         "successText": "您已加入候补名单 — OpenCode Connect 准备就绪时我们会通过邮件通知您。",
         "joinButton": "加入候补名单",
         "alertTitle": "加入候补名单",
-        "fallbackMessage": "无法连接注册服务或打开邮件应用。请发送邮件至 support@agentlabs.cc，主题为 \"OpenCode Connect Waitlist\"。"
+        "queuedText": "已保存在此设备上 — 联网后我们会自动完成注册，你无需再做任何操作。",
+        "emailUsLink": "仍然无法注册？改为给我们发邮件",
+        "emailUsButton": "发送邮件",
+        "queueFailedMessage": "无法连接注册服务，也无法在此设备上保存你的请求。你可以改为给我们发邮件，我们会手动将你加入名单。",
+        "noMailAppMessage": "没有可用的邮件应用。请发送邮件至 support@agentlabs.cc，主题为 \"OpenCode Connect Waitlist\"。"
       },
       "advanced": {
         "backToQuick": "简易模式",