feat(mcp): add delete_dashboard tool

[aminghadersohi]

SUMMARY

Adds a delete_dashboard tool to the Superset MCP service. AI agents that generate test dashboards (e.g. via generate_dashboard) previously had no way to clean them up — this closes that CRUD gap.

Design:

• Params: dashboard_id (int) and a required confirm boolean safety gate. The tool refuses with a clear error unless confirm=true is explicitly passed, forcing the caller (LLM) to state destructive intent. Single delete only — no bulk.
• Backed by the existing DeleteDashboardCommand, so ownership checks, the report-schedule guard, and transactional semantics are identical to the REST API delete path.
• The dashboard is fetched first so the response echoes what was deleted (id, title, slug) in a structured DeleteDashboardResponse with deleted: bool and an error field. Title/slug are sanitized before LLM exposure, matching the other dashboard tools.
• Structured error responses for: not confirmed, not found, forbidden (DashboardForbiddenError), and delete failure (including associated alerts/reports).
• Tool is tagged mutate with class_permission_name="Dashboard", method_permission_name="write", and MCP annotations readOnlyHint=False, destructiveHint=True.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A — backend MCP tool only, no UI changes.

TESTING INSTRUCTIONS

1. pytest tests/unit_tests/mcp_service/dashboard/tool/test_delete_dashboard.py
2. Or manually: start the MCP service, call delete_dashboard with {"dashboard_id": <id>, "confirm": false} and verify it refuses; retry with "confirm": true and verify the dashboard is deleted and the response echoes id/title/slug.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

❌ Patch coverage is 42.62295% with 35 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.17%. Comparing base (f79a88c) to head (97d20ac).
⚠️ Report is 13 commits behind head on master.

Files with missing lines	Patch %	Lines
...set/mcp_service/dashboard/tool/delete_dashboard.py	21.62%	29 Missing ⚠️
superset/mcp_service/dashboard/schemas.py	73.91%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #40956      +/-   ##
==========================================
- Coverage   64.19%   64.17%   -0.02%     
==========================================
  Files        2655     2656       +1     
  Lines      143925   143986      +61     
  Branches    33181    33185       +4     
==========================================
+ Hits        92386    92408      +22     
- Misses      49919    49956      +37     
- Partials     1620     1622       +2     

Flag	Coverage Δ
hive	39.46% <42.62%> (+<0.01%)	⬆️
mysql	58.17% <42.62%> (-0.02%)	⬇️
postgres	58.24% <42.62%> (-0.02%)	⬇️
presto	41.05% <42.62%> (+<0.01%)	⬆️
python	59.71% <42.62%> (-0.03%)	⬇️
sqlite	57.86% <42.62%> (-0.02%)	⬇️
unit	100.00% <ø> (ø)

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