feat(palette): add read-only v002.1 navigation commands

[hkimw]

Summary

• add four PCCX command-palette entries for v002.1 navigation
• route KV260 status through the existing read-only panel
• open the KV260 runbook, project board URL, and trace pipeline doc via VS Code external URL navigation only

Guardrails

• no new process execution path
• no validation allowlist changes
• no GitHub Projects API access
• no publishing metadata or release claim

Refs #126, #127, pccxai/pccx-FPGA-NPU-LLM-kv260#82, pccxai/pccx-lab#166

Validation

• node editors/vscode-prototype/test/extension-manifest.test.mjs
• node editors/vscode-prototype/test/extension-entrypoint.test.mjs
• node editors/vscode-prototype/test/command-handlers.test.mjs
• node editors/vscode-prototype/test/static-boundary.test.mjs
• node --check editors/vscode-prototype/src/config.mjs
• node --check editors/vscode-prototype/src/extension.mjs
• git diff --check
• for f in editors/vscode-prototype/test/*.test.mjs; do node "$f" || exit 1; done