A crashed language server stayed cached with ready==true: readLoop exited and
drained in-flight calls but never cleared the running flag, and GetServer keyed
reuse on ready alone. Every subsequent hover/definition/references then passed
the running guard, wrote to a dead stdin, and blocked the full request timeout —
permanently, since active use kept the server off the idle reaper. A single
crash wedged that language at ~10s/call with no self-heal.
- readLoop now flips running=false on exit, so Call fails fast instead of hanging.
- GetServer treats ready && client.IsRunning() as the liveness condition; a stale
entry is evicted (closed async — its process has already exited) and a fresh
server is spawned in its place.
- drainPending's send is now non-blocking, matching the dispatch path, so a
duplicate-id race can't deadlock it under c.mu.
Test (proven to fail without the fix): a client whose process exits is marked
not-running and its next Call fails fast rather than blocking.
drainStderr discarded all server stderr, so an LSP init failure (e.g. 'command not found', missing module) surfaced as an opaque 'initialization failed'. Retain a bounded tail (StderrCaptureMax=4096B, oldest dropped) under a mutex and attach it to the init-failure error context. Adds TestClientStderrCapture.
lukaszraczylo