feat(plugins): Orca plugin system — kernel, content packs, panels, workers, marketplace v0 (experimental)

Adds Orca's experimental plugin system behind a settings flag: a
supervised kernel, declarative content packs (VM recipes, commands and
keybindings, language packs), sandboxed iframe panels, forked worker
hosts, and a Git-backed marketplace v0 with consent, provenance and
kill-list enforcement.

Theme, icon-theme and terminal-theme contributions are deferred to a
follow-up pass.

src/main/plugins/plugin-host-runtime.ts

@@ -0,0 +1,210 @@
+import { join } from 'node:path'
+import { pathToFileURL } from 'node:url'
+import {
+  pluginWorkerParentMessageSchema,
+  type PluginWorkerChildMessage
+} from '../../shared/plugins/plugin-host-protocol'
+import type { PluginEventName } from '../../shared/plugins/plugin-manifest'
+
+/**
+ * Message-loop core of the out-of-process plugin worker. Electron-free and
+ * side-effect-free (send/import/exit are injected) so it unit-tests without
+ * forking a real child process; `plugin-host-entry.ts` wires it to the fork
+ * IPC channel.
+ */
+
+export type PluginHostCallError = Error & { code?: string }
+
+/** API surface handed to a plugin's `activate(orca)` export. Everything is
+ *  EXPERIMENTAL until pluginApi v1 freezes. */
+export type PluginWorkerOrcaApi = {
+  /** Register the handler for a command declared in the manifest. */
+  commands: {
+    register(commandId: string, handler: (args: unknown) => unknown | Promise<unknown>): void
+  }
+  /** Handle an event the manifest subscribed to (`contributes.events`). */
+  events: {
+    on(event: PluginEventName, handler: (payload: unknown) => void | Promise<void>): void
+  }
+  /** Call a host API method (capability-gated host-side). */
+  host: {
+    call(method: string, params?: unknown): Promise<unknown>
+  }
+  /** Consented capability kinds (informational — the host re-gates). */
+  grantedCapabilities: readonly string[]
+  log(message: string): void
+}
+
+export type PluginWorkerRuntimeOptions = {
+  send: (message: PluginWorkerChildMessage) => void
+  importModule?: (specifier: string) => Promise<unknown>
+  exit?: (code: number) => void
+}
+
+export type PluginWorkerRuntime = {
+  handleMessage(raw: unknown): Promise<void>
+}
+
+function toErrorMessage(error: unknown): string {
+  return error instanceof Error ? (error.stack ?? error.message) : String(error)
+}
+
+export function createPluginWorkerRuntime(
+  options: PluginWorkerRuntimeOptions
+): PluginWorkerRuntime {
+  const send = options.send
+  const importModule = options.importModule ?? ((specifier: string) => import(specifier))
+  const exit = options.exit ?? ((code: number) => process.exit(code))
+  const commandHandlers = new Map<string, (args: unknown) => unknown | Promise<unknown>>()
+  const eventHandlers = new Map<string, ((payload: unknown) => void | Promise<void>)[]>()
+  const pendingHostCalls = new Map<
+    number,
+    { resolve: (value: unknown) => void; reject: (error: PluginHostCallError) => void }
+  >()
+  let nextHostCallId = 0
+  let initialized = false
+  let shuttingDown = false
+  let deactivate: (() => unknown | Promise<unknown>) | null = null
+
+  async function handleInit(input: {
+    pluginRoot: string
+    mainEntry: string
+    grantedCapabilities: string[]
+  }): Promise<void> {
+    if (initialized) {
+      send({ type: 'log', level: 'warn', message: 'ignoring duplicate init message' })
+      return
+    }
+    initialized = true
+    // Why: file URL import keeps ESM plugin entries working on Windows paths.
+    // Why: manifest paths accept either portable separator; split explicitly
+    // so a Windows-authored plugin also imports on macOS/Linux and vice versa.
+    const entryUrl = pathToFileURL(join(input.pluginRoot, ...input.mainEntry.split(/[\\/]/))).href
+    const module = (await importModule(entryUrl)) as { default?: unknown; deactivate?: unknown }
+    const activate = module?.default
+    if (typeof activate !== 'function') {
+      throw new Error(`plugin entry ${input.mainEntry} has no default-exported activate function`)
+    }
+    if (module.deactivate !== undefined && typeof module.deactivate !== 'function') {
+      throw new Error(`plugin entry ${input.mainEntry} has a non-function deactivate export`)
+    }
+    deactivate = (module.deactivate as (() => unknown | Promise<unknown>) | undefined) ?? null
+    const orca: PluginWorkerOrcaApi = {
+      commands: {
+        register(commandId, handler) {
+          commandHandlers.set(commandId, handler)
+        }
+      },
+      events: {
+        on(event, handler) {
+          const handlers = eventHandlers.get(event) ?? []
+          handlers.push(handler)
+          eventHandlers.set(event, handlers)
+        }
+      },
+      host: {
+        call(method, params) {
+          const callId = nextHostCallId++
+          return new Promise<unknown>((resolve, reject) => {
+            pendingHostCalls.set(callId, { resolve, reject })
+            send({ type: 'hostCall', callId, method, params })
+          })
+        }
+      },
+      grantedCapabilities: input.grantedCapabilities,
+      log(message) {
+        send({ type: 'log', level: 'info', message: String(message).slice(0, 8192) })
+      }
+    }
+    await activate(orca)
+    send({ type: 'ready', commands: [...commandHandlers.keys()] })
+  }
+
+  return {
+    async handleMessage(raw) {
+      const parsed = pluginWorkerParentMessageSchema.safeParse(raw)
+      if (!parsed.success) {
+        send({ type: 'log', level: 'warn', message: 'ignoring malformed parent message' })
+        return
+      }
+      const message = parsed.data
+      try {
+        switch (message.type) {
+          case 'init': {
+            await handleInit(message)
+            return
+          }
+          case 'invokeCommand': {
+            const handler = commandHandlers.get(message.commandId)
+            if (!handler) {
+              send({
+                type: 'commandResult',
+                callId: message.callId,
+                ok: false,
+                error: `no handler registered for command ${message.commandId}`
+              })
+              return
+            }
+            try {
+              const value = await handler(message.args)
+              send({ type: 'commandResult', callId: message.callId, ok: true, value })
+            } catch (error) {
+              send({
+                type: 'commandResult',
+                callId: message.callId,
+                ok: false,
+                error: toErrorMessage(error)
+              })
+            }
+            return
+          }
+          case 'deliverEvent': {
+            const handlers = eventHandlers.get(message.event) ?? []
+            for (const handler of handlers) {
+              try {
+                await handler(message.payload)
+              } catch (error) {
+                send({ type: 'log', level: 'error', message: toErrorMessage(error) })
+              }
+            }
+            send({ type: 'eventAck', eventId: message.eventId })
+            return
+          }
+          case 'hostResult': {
+            const pending = pendingHostCalls.get(message.callId)
+            if (!pending) {
+              return
+            }
+            pendingHostCalls.delete(message.callId)
+            if (message.ok) {
+              pending.resolve(message.value)
+            } else {
+              const error: PluginHostCallError = new Error(message.error ?? 'host call failed')
+              error.code = message.errorCode
+              pending.reject(error)
+            }
+            return
+          }
+          case 'shutdown': {
+            if (shuttingDown) {
+              return
+            }
+            shuttingDown = true
+            try {
+              await deactivate?.()
+            } catch (error) {
+              send({ type: 'log', level: 'error', message: toErrorMessage(error).slice(0, 8192) })
+            }
+            exit(0)
+          }
+        }
+      } catch (error) {
+        // Why: an init/activation failure leaves the worker useless; report
+        // and die so the parent surfaces the error instead of hanging on
+        // the ready timeout.
+        send({ type: 'fatal', error: toErrorMessage(error) })
+        exit(1)
+      }
+    }
+  }
+}