feat(opencode): cut plugin system and remote behavior feeds; add SessionContext assembly and Runner

- delete plugin machinery (loader, install, meta, hooks) and all trigger sites
- fold first-party provider auth into static registry (provider/hooks.ts)
- remove remote instruction URL fetch, skills remote puller, TUI plugin host
- add session/context.ts: single provenance-tagged context assembly point
- add session/runner.ts: admit/context/stream/tools loop with compaction policy
- relocate audit artifacts to audit/ (FORK-AUDIT, instruction docs as evidence)

packages/opencode/src/server/routes/instance/httpapi/handlers/pty.ts

@@ -1,7 +1,6 @@
 import * as InstanceState from "@/effect/instance-state"
 import { registerDisposer } from "@/effect/instance-registry"
 import { InstanceRef, WorkspaceRef } from "@/effect/instance-ref"
-import { Plugin } from "@/plugin"
 import { Pty } from "@opencode-ai/core/pty"
 import { PtyProtocol } from "@opencode-ai/core/pty/protocol"
 import { PtyID } from "@opencode-ai/core/pty/schema"
@@ -42,7 +41,6 @@ export const ptyHandlers = HttpApiBuilder.group(InstanceHttpApi, "pty", (handler
   Effect.gen(function* () {
     const tickets = yield* PtyTicket.Service
     const cors = yield* CorsConfig
-    const plugin = yield* Plugin.Service
     const locations = yield* LocationServiceMap.Service
     const unregister = registerDisposer((directory) =>
       Effect.runPromise(locations.invalidate(Location.Ref.make({ directory: AbsolutePath.make(directory) }))),
@@ -68,14 +66,13 @@ export const ptyHandlers = HttpApiBuilder.group(InstanceHttpApi, "pty", (handler
 
     const create = Effect.fn("PtyHttpApi.create")(function* (ctx: { payload: typeof Pty.CreateInput.Type }) {
       const cwd = ctx.payload.cwd || (yield* InstanceState.context).directory
-      const shell = yield* plugin.trigger("shell.env", { cwd }, { env: {} as Record<string, string> })
       return yield* pty(
         Pty.Service.use((service) =>
           service.create({
             ...ctx.payload,
             args: ctx.payload.args ? [...ctx.payload.args] : undefined,
             cwd,
-            env: { ...ctx.payload.env, ...shell.env },
+            env: { ...ctx.payload.env },
           }),
         ),
       )

packages/opencode/src/server/routes/instance/httpapi/server.ts

@@ -20,7 +20,6 @@ import { LSP } from "@/lsp/lsp"
 import { MCP } from "@/mcp"
 import { McpAuth } from "@/mcp/auth"
 import { Permission } from "@/permission"
-import { Plugin } from "@/plugin"
 import { PluginPtyEnvironment } from "@/plugin/pty-environment"
 import { InstanceStore } from "@/project/instance-store"
 import { Project } from "@/project/project"
@@ -42,7 +41,6 @@ import { Todo } from "@/session/todo"
 import { SessionShare } from "@/share/session"
 import { ShareNext } from "@/share/share-next"
 import { Skill } from "@/skill"
-import { Discovery } from "@/skill/discovery"
 import { Snapshot } from "@/snapshot"
 import { Storage } from "@/storage/storage"
 import { ToolRegistry } from "@/tool/registry"
@@ -219,13 +217,11 @@ const app = LayerNode.group([
   Ripgrep.node,
   Storage.node,
   Snapshot.node,
-  Plugin.node,
   ModelsDev.node,
   Provider.node,
   ProviderAuth.node,
   Agent.node,
   Skill.node,
-  Discovery.node,
   Question.node,
   Permission.node,
   PermissionSaved.node,