Blip 2.1.0 — war room

Ten expert-lens reviewers swept the repo after the DHH retweet; 114
findings, the clear ones fixed here, the rest on the roadmap.

Fixed — correctness

• Attachment-cache eviction had silently never run since 1.9.4 (a missing
  statSync import threw inside the LRU). 500 MB cap is real again.
• A DM thread admitted that person's messages from group chats.
• Catch-up fetches could exceed Bun's default 1 MB spawnSync buffer and
  fail sticky; all bridge calls now allow 64 MB.
• A timed-out imsg (Mac asleep behind a live ssh mux) read as a bridge
  bug; it now reads as "Mac asleep" and greys the icon.
• Bridge errors show the last stderr line (Python puts the cause last),
  not "Traceback (most recent call last):".
• state.json is fsync'd before rename (a power cut no longer resets every
  read mark). Cache temp names carry entropy (no EEXIST after pid reuse).
• Link cards: $null titles, URLs with (…) (Wikipedia), and userinfo
  host-spoofing handled. Inline-reply snippets respect Recently Deleted.
• macOS 12 and earlier: imsg no longer dies on the missing
  Recently-Deleted table.
• Avatar initials for whitespace-only names; non-ASCII attachment names
  survive sanitizing; sent files keep their extension.
• wait_for_copy matches only attachment rows newer than the send
  (same-name re-sends no longer confuse it); a send whose copy was never
  observed is kept in ~/.blip/sent instead of deleted an hour later.

Fixed — security / privacy

• File-send captions no longer appear in any process's argv
  (--caption-stdin). A cut ssh stream can no longer deliver a truncated
  file (--file-bytes N is enforced on the Mac).
• Cache file extensions follow the gated MIME type, not the sender's
  filename (xdg-open dispatches on extension).
• tcc-check removed from the confined key's allowlist.
• blip-setup no longer sources bridge.conf, no longer echoes a message
  body into the terminal, guards the authorized_keys append with a
  newline, keeps a hand-set automation= on re-run, drops the ssh master
  before re-checking grants, and names a missing Xcode CLT instead of
  misdiagnosing Full Disk Access. install.sh fails loudly on the CLT stub.
• Consent banner prints only on a TTY (recipients no longer reach journald).
• A real phone number and email were removed from a public test fixture.
• Transient bridge failures no longer write a 7-day "no photo" marker.

Changed

• Users' dashes are sent as typed (--keep-dashes everywhere).
• xdg-open and the window-state writer run detached (a blocking handler
  or a mid-write hide could swallow later clicks / the hidden state).
• IPC compose refuses when the popout is closed.
• The shim's offline message includes the ssh reason.
• sync-bridge.sh stages upstream copies beside locally-modified tools
  instead of overwriting them.
• Tests are isolated from the developer's real caches (bunfig.toml
  preload sets XDG_CACHE_HOME).