fix: resolve publish blockers for v3.7.4→v3.8.0 release

- Fix #1991 crash: optional chaining for task-history sessionID access
- Fix #1992 think-mode: add antigravity entries to HIGH_VARIANT_MAP
- Fix #1949 Copilot premium misattribution: use createInternalAgentTextPart
- Fix #1982 load_skills: pass directory to discoverSkills for project-level skills
- Fix command priority: sort scopePriority before .find(), project-first return
- Fix Google provider transform: apply in userFallbackModels path
- Fix ralph-loop TUI: optional chaining for event handler
- Fix runtime-fallback: unify dual fallback engines, remove HTTP 400 from retry,
  fix pendingFallbackModel stuck state, add priority gate to skip model-fallback
  when runtime-fallback is active
- Fix Prometheus task system: exempt from todowrite/todoread deny
- Fix background_output: default full_session to true
- Remove orphan hooks: hashline-edit-diff-enhancer (redundant with hashline_edit
  built-in diff), task-reminder (dead code)
- Remove orphan config entries: 3 stale hook names from Zod schema
- Fix disabled_hooks schema: accept arbitrary strings for forward compatibility
- Register json-error-recovery hook in tool-guard pipeline
- Add disabled_hooks gating for question-label-truncator, task-resume-info,
  claude-code-hooks
- Update test expectations to match new behavior

src/features/background-agent/spawner.ts

@@ -1,7 +1,7 @@
 import type { BackgroundTask, LaunchInput, ResumeInput } from "./types"
 import type { OpencodeClient, OnSubagentSessionCreated, QueueItem } from "./constants"
 import { TMUX_CALLBACK_DELAY_MS } from "./constants"
-import { log, getAgentToolRestrictions, promptWithModelSuggestionRetry } from "../../shared"
+import { log, getAgentToolRestrictions, promptWithModelSuggestionRetry, createInternalAgentTextPart } from "../../shared"
 import { subagentSessions } from "../claude-code-session-state"
 import { getTaskToastManager } from "../task-toast-manager"
 import { isInsideTmux } from "../../shared/tmux"
@@ -146,7 +146,7 @@ export async function startTask(
         question: false,
         ...getAgentToolRestrictions(input.agent),
       },
-      parts: [{ type: "text", text: input.prompt }],
+      parts: [createInternalAgentTextPart(input.prompt)],
     },
   }).catch((error) => {
     log("[background-agent] promptAsync error:", error)
@@ -230,7 +230,7 @@ export async function resumeTask(
         question: false,
         ...getAgentToolRestrictions(task.agent),
       },
-      parts: [{ type: "text", text: input.prompt }],
+      parts: [createInternalAgentTextPart(input.prompt)],
     },
   }).catch((error) => {
     log("[background-agent] resume prompt error:", error)