0.16.0 — a server started in its workspace, pipelined call-hierarchy batches

Source break, and the fix

• lsp::LspError has a new variant, WorkingDir { dir, source }. An exhaustive match adds it.

Added

• lsp::Client::new_stdio_in(command, dir): starts the server in dir, so a toolchain manager's
  proxy (rustup) reads the workspace's rust-toolchain.toml. A dir that is not a directory is
  refused with LspError::WorkingDir before anything starts. The server does not inherit
  RUSTUP_TOOLCHAIN: rustup ranks it above every toolchain file, and rustup's cargo proxy sets it
  for every process cargo runs, so a caller under cargo run or cargo test would otherwise hand
  the server cargo's toolchain.
• lsp::Client::new_stdio_in_with_env(command, dir, envs): new_stdio_in, with envs set on top
  of the inherited environment — for a server whose per-user state, such as a cache under its home
  directory, the caller decides. A RUSTUP_TOOLCHAIN named in envs is set.
• lsp::Client::prepare_call_hierarchy_many(queries, in_flight) with lsp::PositionQuery, and
  lsp::Client::outgoing_calls_many(targets, in_flight): up to in_flight requests outstanding on
  one server, answers matched to questions by request id, one outcome per input in input order,
  each with the single call's retry and error discipline. Changing an open document's text waits
  until every earlier request is answered.

Tests

• The real-server tier is #[ignore]d: a plain cargo test reports those cases as ignored
  instead of passing them after an early return. Run them with BAGE_LSP_REAL_TEST=1 cargo test --lib --test lsp_session --test lsp_hierarchy --test lsp_pipeline --test lsp_typing_acquisition -- --ignored; selected without the variable or a server, they fail.