[fylorn]

Core says everything it has to say in English now, and the sentences it sends to
a client carry a stable code beside them. The desktop app needs a tag to pin
before it can read any of it.

What changed for anyone reading the protocol

• Every human-readable sentence is a Msg — a code, the arguments that fill
  it, and the English text — rather than a String.
  Event::RequestFailed.message, ProxyChanged.detail, L1Result.error and
  HistoryRow.error are all Msg now. ProxyChanged also gained failed, the
  stage the connection got stuck at.
• A control-plane error responds with a JSON Msg rather than a plain-text
  body.
• The synthesized default route is default and its catch-all rule is
  catch-all, not 默认 and 兜底.
• The request store gained error_code and error_args (schema 13), so a
  failure keeps its code when the app reads history back.
• tw-adopt writes English markers and English field names into the user's own
  files, and tw-scan's built-in rules have English ids and reasons.

Two things do not survive the upgrade. A client adopted by 0.9.x cannot be
restored by 0.10 — its markers and its sidecar record use the old names. And an
override file that disables a built-in scan rule by its old Chinese id reports
that the id is unknown.

CONTROL_API_VERSION goes to 2 for all of it. A client built against 1 would
render these as strings — a screenful of JSON — so it is better that it refuses
at the handshake and says to rebuild.

In this release

#53, #54, #55, #56, #57, #58, plus #52 which made main the branch the
contract describes.

Verified

cargo fmt --all -- --check, cargo clippy --workspace --all-targets -- -D warnings, cargo test --workspace (78 suites, 0 failures) and
./scripts/smoke.sh (51 passed, 0 failed).

🤖 Generated with Claude Code