[FEATURE] scheduled-tasks MCP: expose model + effort on create/update_scheduled_task, and make them readable

### Preflight Checklist

- [x] I have searched [existing requests](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20label%3Aenhancement) and this feature hasn't been requested yet
- [x] This is a single feature request (not multiple features)

### Problem Statement

First, genuine thanks — scheduled tasks are the feature that turned Claude Code from something I use into something that works while I sleep. Thirty of them run my week. This request comes from leaning on them hard.

**The gap:** a scheduled task runs on whatever the app's current default model is, and the session that creates and maintains those tasks can neither set that nor read it. The `scheduled-tasks` MCP tools (`create_scheduled_task`, `update_scheduled_task`, `list_scheduled_tasks`) expose taskId, prompt, description, cron/fireAt, enabled and notifyOnCompletion — nothing about model or effort. Task `SKILL.md` frontmatter accepts only `name` and `description`. The per-task dropdown in the desktop Edit form is a human-only lever.

**Concrete, from a 30-task fleet** (macOS, desktop 1.24012.9, claude-code 2.1.219, individual Max account). None of the 30 has an explicit per-task model. Reading what they actually ran — `message.model` plus the sibling top-level `effort` key in `~/.claude/projects/**/.jsonl` — every task ran `claude-opus-4-8` @ `high` through 2026-07-24, then `claude-opus-5` @ `high` from 2026-07-25. The whole fleet re-tiered in lockstep on a default change, unannounced. Some of those tasks are trivial pollers that belong on Haiku; some are reasoning-heavy audits that belong at the top tier and xhigh effort. Neither can be expressed.

This was asked once before, as #62337, and was auto-closed by the duplicate bot on the day it was filed (state "completed", 0 reactions, now locked) against two *bug* reports about the UI dropdown being ignored — a related but different problem. Re-filing with the effort dimension and the read-back added.

### Proposed Solution

1. **Add optional `model` and `effort`** to `create_scheduled_task` and `update_scheduled_task`, using the same enums the Agent/Task tool already accepts. Omitted = exactly today's behavior, so nothing existing changes.
2. **Return them from `list_scheduled_tasks`**, so a session can audit a whole fleet without doing transcript forensics.
3. **Honor `model:` / `effort:` in a task's SKILL.md frontmatter** (currently stripped), so a task's tier lives beside its prompt and is version-controllable.
4. Ideally, an explicit `"default"` sentinel that is distinct from unset — so "follow the app default" becomes a choice a user made, rather than the absence of one.

### Alternative Solutions

- **`settings.json` `model` / `effortLevel`** — global, so it re-tiers every interactive session too. Wrong granularity.
- **The per-task dropdown in the desktop Edit form** — works (per the 2026-07-08 report in #68924), but it is manual, does not scale to 30 tasks, and cannot be audited or bulk-corrected by the agent that manages them.
- **Delegating inside the prompt** — have the task immediately hand its work to a subagent with a `model` override. This is my current workaround and it does work, but it pays for a top-tier orchestrator turn just to perform the handoff, and it cannot lower the effort of the task session itself.
- **Parsing `~/.claude/projects/**/*.jsonl` after the fact** — good enough for observability, since model and effort are both recorded there, but it is forensics rather than configuration: it can only tell you what already ran, at whatever tier it already cost.

### Priority

Medium - Would be very helpful

### Feature Category

MCP server integration

### Use Case Example

1. `gmail-triage-3day` — classify ~40 emails against a fixed rubric, three times a week. Wants Haiku at low effort. Currently runs on the top tier.
2. `rebuild-audit-weekly` — a subtractive audit across a large document tree where a wrong call is expensive to undo. Wants the strongest model at xhigh. Also runs at whatever the default happens to be that week.
3. Fleet audit: *"Claude, list any scheduled task that isn't on my chosen model and effort, and fix them."* Impossible today at both ends — cannot read, cannot set.

### Additional Context

Related issues: #62337 (this ask, bot-closed same-day, locked, 0 votes) · #36496 (per-task dropdown ignored — the older bug) · #68924 (individual-account default model) · #43326 (auto-select model/effort by complexity) · #43083 (configurable effort for subagents — the sibling surface where this was already requested).

The asymmetry that makes this read as an oversight rather than a decision: the Agent/Task tool already accepts both `model` and `effort` per call. Scheduled tasks are the one agent-spawning surface that does not — and they are the surface where it matters most, because nobody is watching when they fire.

Environment: macOS (Darwin 25.5.0), Claude desktop app 1.24012.9, claude-code 2.1.219, individual Max account, 30 active scheduled tasks.

Start by comparing the scheduled-tasks MCP tool interfaces with the Agent/Task tool's existing model and effort inputs, then inspect how task SKILL.md frontmatter and settings.json are handled. Done means create, update, and list support the requested values, frontmatter is honored, and omitted values preserve current behavior; the issue does not name implementation files or tests.

Written by the indexing model from the issue text.