[FEATURE] No setting to disable unused beta tool schemas (Workflow/Artifact/DesignSync/Cron/worktrees) inflating context

### 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

"System tools" schemas for beta features (Workflow orchestration, Artifacts publishing, DesignSync, RemoteTrigger/cron scheduling, cross-session messaging, git worktrees) load into every session's context based on account-level GrowthBook flags (visible in ~/.claude.json under cachedGrowthBookFeatures, e.g. tengu_workflows_enabled, tengu_kairos_cron, tengu_worktree_mode), regardless of whether the session ever uses them. In a session doing plain OpenAPI/Swagger spec review, /context showed "System tools" consuming 52.4k of 200k tokens (26.2%) before any actual work began. There's no settings.json key to opt a session out of specific built-in tool schemas, so accounts with more beta flags enabled carry permanently higher context overhead than colleagues on fewer flags, with no way to equalize it.

### Proposed Solution

Add a settings.json key (e.g. "disabledTools": ["Workflow", "Artifact", "DesignSync", "RemoteTrigger", "CronCreate"]) that excludes the named built-in tools' schemas from the system prompt for a given project/session — similar to existing per-project MCP server scoping. Ideally also surfaced in /config as per-capability toggles (Workflows/Ultracode, Artifacts, Design Sync, Scheduled routines, cross-session messaging, worktrees) so users can trade a feature off against context budget without waiting on an account-level flag change.

### Alternative Solutions

None available today. Checked both global and project settings.json for a tool-exclusion mechanism — none exists. The tool manifest is driven entirely by cachedGrowthBookFeatures in ~/.claude.json, which isn't user-editable.

### Priority

High - Significant impact on productivity

### Feature Category

Configuration and settings

### Use Case Example

1. Working in a small API-documentation repo (OpenAPI/Swagger registry), task is spec linting and audit review only.
2. /context shows System tools at 52.4k/200k tokens (26.2%) before any work starts, because Workflow, Artifact, DesignSync, RemoteTrigger, CronCreate, and worktree tools are all loaded due to account flags.
3. None of those tools are relevant to spec-linting work.
4. A disabledTools setting would let this project reclaim ~50k tokens of working context per session, instead of losing it permanently to features that are never invoked.

### Additional Context

Evidence gathered while investigating: ~/.claude.json → cachedGrowthBookFeatures shows tengu_workflows_enabled: true, tengu_kairos_cron: true, tengu_worktree_mode: true (plus similarly-gated flags for Artifact/DesignSync/RemoteTrigger). /context breakdown for comparison: System tools 52.4k tokens (26.2%) vs. Memory files 5.1k (2.5%) and Skills 2.8k (1.4%) — tool schemas dominate fixed overhead by a wide margin over everything else in the budget.

Start by comparing the global and project settings.json files with ~/.claude.json and its cachedGrowthBookFeatures entries. Use /context to reproduce the System tools overhead and /config to inspect existing configuration controls. Done means a documented per-project or per-session way to exclude selected built-in tool schemas and verify that the excluded schemas no longer consume context.

Written by the indexing model from the issue text.