fix(arcade-mcp-server): drop old key on prompt rename in update_prompt

[pmdroid]

What

PromptManager.update_prompt verified that a prompt existed under the input name, then upserted the new handler under prompt.name. When prompt.name differs from name — a rename — the entry under the old name was never removed, so the registry kept a stale, orphaned prompt. ResourceManager.update_resource already does this correctly.

This change mirrors update_resource: it removes by the old name first (which also serves as the existence check, raising NotFoundError when the prompt is missing), then upserts by prompt.name.

Why

Found while reviewing the in-progress TypeScript port, where the same bug had been faithfully reproduced. The TS side has been fixed in parallel; this PR fixes the Python original so the two stay aligned.

Tests

Added two regression tests in libs/tests/arcade_mcp_server/test_prompt.py:

• test_update_prompt_rename_does_not_orphan_old_entry
• test_update_prompt_missing_raises_not_found

uv run pytest libs/tests/arcade_mcp_server/test_prompt.py — 16 passed. ruff check / ruff format --check clean.

Closes PLT-2067.

🐕 Written by Kyoto, an AI agent, on Pascal's behalf —

---

Note

Low Risk
Small, localized registry fix with tests; no auth, data, or API surface changes beyond correct prompt rename behavior.

Overview
Fixes a registry bug where renaming a prompt via update_prompt left the old name registered alongside the new one.

PromptManager.update_prompt now removes the entry under the original name before upserting under prompt.name, matching how ResourceManager.update_resource handles URI changes. Missing prompts still raise NotFoundError via the remove step.

Adds regression tests for rename (single listing, old name not found) and update of a non-existent prompt.

^{Reviewed by Cursor Bugbot for commit 7ebdcda. Bugbot is set up for automated code reviews on this repo. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
...de-mcp-server/arcade_mcp_server/managers/prompt.py	94.82% <100.00%> (+12.06%)	⬆️

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.