HTTP API with SSE streaming

[JaimeStill]

Context

Part of Objective #2 (Kernel Interface). Pure HTTP handlers with SSE streaming replace ConnectRPC. Follows agent-lab patterns (~/code/agent-lab). The kernel serves GET /openapi.json for schema documentation.

Depends on: #26 (Multi-session kernel)

Scope

New api/ package replacing rpc/. Pure HTTP handlers with SSE streaming.

• Remove ConnectRPC: Delete rpc/gen/, rpc/proto/, rpc/buf.yaml, rpc/buf.gen.yaml. Remove connectrpc.com/connect and google.golang.org/protobuf from go.mod.
• Request/response types: Go structs with JSON tags as source of truth
• HTTP handlers:
  • GET /agents — List registered agents and capabilities
  • POST /sessions — Create session (agent name, bootstrap context)
  • GET /sessions/{id} — Get session metadata and status
  • POST /sessions/{id}/run — Submit prompt → SSE stream
  • GET /sessions/{id}/memory — List memory keys
  • GET /sessions/{id}/memory/{key...} — Get memory entry
  • PUT /sessions/{id}/memory/{key...} — Save memory entry
  • DELETE /sessions/{id}/memory/{key...} — Delete memory entry
  • GET /tools — List registered tools
  • GET /openapi.json — OpenAPI spec
• SSE streaming: Typed events (status, tool_call, token), JSON data, flush per event, [DONE] marker
• Response helpers: RespondJSON(), RespondError()
• Error mapping: Kernel errors → HTTP status codes
• Handler tests: Using httptest.NewServer and SSE client parsing
• OpenAPI spec: Endpoint definitions managed alongside handlers

Approach

Follow agent-lab patterns:

• api/handler.go — Handler struct with kernel dependency, Routes method
• api/types.go — Request/response Go structs
• api/respond.go — JSON and error response helpers
• api/sse.go — SSE streaming utility
• api/openapi.go — OpenAPI spec construction

Acceptance Criteria

• ConnectRPC removed (rpc/ deleted, dependencies removed from go.mod)
• All HTTP endpoints implemented and tested
• SSE streaming works for /run endpoint
• OpenAPI spec served at /openapi.json
• Error mapping from kernel to HTTP status codes
• Handler tests with httptest
• go vet ./... passes