chore: add prettier auto-format hook for Claude Code

[dqnykamp]

Summary

• Adds .claude/settings.json with a PostToolUse hook that runs prettier --write --ignore-unknown on files after Write/Edit/MultiEdit/NotebookEdit operations.
• Enforces automatic formatting rather than relying on the agent to read and follow the "format with prettier before committing" instruction in CLAUDE.md — which was missed in refactor(worker-javascript): extract Phase 1 helpers from Core.js #1036.
• Hook respects .prettierignore (auto-discovered by prettier) and only formats files inside the project directory.

Test plan

• After merging, contributors using Claude Code on this repo should open /hooks once (or restart Claude Code) so the new settings take effect.
• Verify by editing a .ts/.js file with formatting violations and confirming it gets auto-formatted on save.
• Confirm .md and other ignored paths are skipped (already covered by .prettierignore).

🤖 Generated with Claude Code

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[Copilot]

Pull request overview

Adds a Claude Code hook configuration to automatically run Prettier after file write/edit operations, aiming to keep agent-driven edits consistently formatted in this repo.

Changes:

• Add .claude/settings.json defining a PostToolUse hook for Write|Edit|MultiEdit|NotebookEdit.
• Hook runs npx --no-install prettier --write --ignore-unknown on the edited file path (when it appears to be under $PWD).

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[Copilot]

The PR description mentions relying on an instruction in CLAUDE.md, but there is no CLAUDE.md in this repository (the existing guidance appears to be in AGENTS.md). Please update the description to reference the correct file so future contributors can find the formatting requirement.

[Copilot]

The stderr redirection (2>/dev/null) is applied to the { ... } block but not to the jq command. If jq is missing or errors, it can still print noise to stderr even though the hook ultimately succeeds due to || true. Consider redirecting jq stderr as well (or checking for jq before running) so hook output stays clean.

Suggested change

	"command": "jq -r '.tool_response.filePath // .tool_input.file_path' | { read -r f; case \"$f\" in \"$PWD\"/*) npx --no-install prettier --write --ignore-unknown \"$f\" ;; esac; } 2>/dev/null || true",
	"command": "jq -r '.tool_response.filePath // .tool_input.file_path' 2>/dev/null | { read -r f; case \"$f\" in \"$PWD\"/*) npx --no-install prettier --write --ignore-unknown \"$f\" ;; esac; } 2>/dev/null || true",

[Copilot]

The "$PWD" prefix check can be bypassed by paths containing .. segments (e.g., "$PWD/../outside") which still match the case pattern but resolve outside the repo. To enforce “only format files inside the project directory”, normalize with realpath (or an equivalent) before comparing, and only run Prettier when the normalized path is within the normalized repo root.

Suggested change

	"command": "jq -r '.tool_response.filePath // .tool_input.file_path' | { read -r f; case \"$f\" in \"$PWD\"/*) npx --no-install prettier --write --ignore-unknown \"$f\" ;; esac; } 2>/dev/null || true",
	"command": "jq -r '.tool_response.filePath // .tool_input.file_path' | { read -r f; repo_root=$(realpath \"$PWD\") && target=$(realpath \"$f\") && case \"$target\" in \"$repo_root\"|\"$repo_root\"/*) npx --no-install prettier --write --ignore-unknown \"$target\" ;; esac; } 2>/dev/null || true",