feat(mcp): add MCP server, Grafana observability, and script-editor assets

[zachbroad]

Summary

Adds a third binary, cmd/mcp — a stdio Model Context Protocol server exposing read-only list_sources, list_actions, and list_deliveries tools backed by the existing store (github.com/modelcontextprotocol/go-sdk).

Also included:

• docker-compose: add a Grafana service (promotes prometheus/client_golang to a direct dependency)
• web/static: vendor htmx + Monaco editor assets for the script-editor UI
• Makefile: run-mcp target and bin/mcp build
• docs: MCP server guide, tour page, local-dev quickstart section; CLAUDE.md updated to three binaries; Astro nav entries
• go.mod: bump to go 1.25, add go-sdk and supporting deps
• .gitignore: ignore local .superpowers/ tooling state

Notes

• This work is independent of the webhook-auth branch (PR Incoming webhook authentication (HMAC / bearer / token / Ed25519 with provider presets) #4). It was cherry-picked onto main as a single commit; the auth plan doc that isn't present on main was dropped during the cherry-pick.
• go build ./... and go vet ./cmd/mcp/ pass.

🤖 Generated with Claude Code

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: c7390cd6-a6c3-43b5-8744-ad268822a79c

📥 Commits

Reviewing files that changed from the base of the PR and between 8ed5ac0 and 0f711be.

⛔ Files ignored due to path filters (3)

• go.sum is excluded by !**/*.sum
• web/static/htmx.min.js is excluded by !**/*.min.js
• web/static/vs/base/browser/ui/codicons/codicon/codicon.ttf is excluded by !**/*.ttf

📒 Files selected for processing (19)

• .gitignore
• CLAUDE.md
• Makefile
• README.md
• cmd/mcp/main.go
• docker-compose.yml
• docs/astro.config.mjs
• docs/src/content/docs/getting-started/quickstart.md
• docs/src/content/docs/guides/mcp.md
• docs/src/content/docs/tour.md
• go.mod
• web/static/vs/base/worker/workerMain.js
• web/static/vs/basic-languages/javascript/javascript.js
• web/static/vs/basic-languages/typescript/typescript.js
• web/static/vs/editor/editor.main.css
• web/static/vs/editor/editor.main.js
• web/static/vs/language/typescript/tsMode.js
• web/static/vs/language/typescript/tsWorker.js
• web/static/vs/loader.js

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/mcp-server

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