feat: complete Go port with go-te terminal emulator

Full Go implementation under go/ replacing Python pyte with go-te:
- HTTP server with WebSocket protocol, SSE, screenshot SVG rendering
- PTY terminal sessions and Docker exec sessions
- Docker watcher (label-based container discovery + event stream)
- CPU stats collection with sparkline SVG rendering
- Session manager with TwoWayMap routing and replay buffers
- C1 normalization, DA filtering, identity generation, theme palettes

Audit fixes for 9 concurrency/correctness issues:
- HTTP transport leak: shared client pool for Docker socket calls
- WebSocket concurrent writes: all writes routed through send channel
- Closed channel panic: atomic.Bool guard on enqueueWSData
- GetFirstRunningSession: use UnsafeForward under SessionManager lock
- NewSession TOCTOU: re-check routeKey after re-acquiring lock
- waitErr data race: protect with mutex in both session types
- Replay buffer fragmentation: copy to new slice on eviction
- go-te dirty tracking: check screen.Dirty before incrementing counter
- Identity modulo bias: rejection sampling for uniform distribution

All Go tests pass (including -race). Python baseline unchanged (397 tests).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

go/go.sum

@@ -0,0 +1,20 @@
+github.com/clipperhouse/uax29/v2 v2.2.0 h1:ChwIKnQN3kcZteTXMgb1wztSgaU+ZemkgWdohwgs8tY=
+github.com/clipperhouse/uax29/v2 v2.2.0/go.mod h1:EFJ2TJMRUaplDxHKj1qAEhCtQPW2tJSwu5BF98AuoVM=
+github.com/creack/pty v1.1.18 h1:n56/Zwd5o6whRC5PMGretI4IdRLlmBXYNjScPaBgsbY=
+github.com/creack/pty v1.1.18/go.mod h1:MOBLtS5ELjhRRrroQr9kyvTxUAFNvYEK993ew/Vr4O4=
+github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 h1:El6M4kTTCOh6aBiKaUGG7oYTSPP8MxqL4YI3kZKwcP4=
+github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510/go.mod h1:pupxD2MaaD3pAXIBCelhxNneeOaAeabZDe5s4K6zSpQ=
+github.com/gorilla/websocket v1.5.3 h1:saDtZ6Pbx/0u+bgYQ3q96pZgCzfhKXGPqt7kZ72aNNg=
+github.com/gorilla/websocket v1.5.3/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
+github.com/mattn/go-runewidth v0.0.19 h1:v++JhqYnZuu5jSKrk9RbgF5v4CGUjqRfBm05byFGLdw=
+github.com/mattn/go-runewidth v0.0.19/go.mod h1:XBkDxAl56ILZc9knddidhrOlY5R/pDhgLpndooCuJAs=
+github.com/rcarmo/go-te v0.0.0-20260214100434-edf070e453db h1:wJrQ4ABeQey49QEDHbHHZISpXoC5OtIeihEF4WA2M14=
+github.com/rcarmo/go-te v0.0.0-20260214100434-edf070e453db/go.mod h1:cLsrtroxCubS+OHHwH0riB6xeNESfntaHEeI1jPAedk=
+github.com/rivo/uniseg v0.4.7 h1:WUdvkW8uEhrYfLC4ZzdpI2ztxP1I582+49Oc5Mq64VQ=
+github.com/rivo/uniseg v0.4.7/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
+golang.org/x/text v0.34.0 h1:oL/Qq0Kdaqxa1KbNeMKwQq0reLCCaFtqu2eNuSeNHbk=
+golang.org/x/text v0.34.0/go.mod h1:homfLqTYRFyVYemLBFl5GgL/DWEiH5wcsQ5gSh1yziA=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=