feat: add release workflow for multi-target theme distribution

[slowdini]

Summary

Adds a complete release pipeline for distributing Synthpunk themes across all five targets (VS Code, Zed, Neovim, WezTerm, Starship), mirroring the dev → main PR pattern from eval-magic and slow-powers.

What's included

Workflows (.github/workflows/)

• ci.yml — PR gate: biome check + tsc, tests, generator sync check (bun run build then git diff --exit-code on generated files)
• release-pr.yml — Manual trigger with version input: validates format, bumps all manifests via scripts/bump-version.ts, commits to dev, opens dev → main PR with release-notes placeholder
• release.yml — On merge to main: tags vX.Y.Z, creates GitHub Release, builds themes, uploads curl-install files (starship.toml + 4 wezterm TOMLs), builds VSIX, fans out publish jobs (VS Code Marketplace, OpenVSX, Zed, synthpunk.nvim) — each gated on a repo variable so channels without configured secrets are skipped

Version tooling (scripts/)

• manifest-files.ts — single source of truth for version-locked manifests
• bump-version.ts — bumps JSON (parse + stringify + biome format) and TOML (regex replace) manifests; tested with 4 unit tests
• tests/lockstep.test.ts — asserts all manifests match package.json version (3 tests)

Pre-release cleanup

• Root package.json: name synthpunk, version 0.1.0, license MIT, build script with biome format step
• biome.json: json.formatter.enabled: true for consistent JSON formatting
• LICENSE (MIT), README.md (root, with per-target curl-install commands), RELEASE.md (manual publishing catalogue), AGENTS.md
• themes/vscode/.vscodeignore, themes/vscode/package.json repository field
• themes/zed/extension.toml: fix id (synthpunk), name, repo URL
• Fix stale regen commands in 4 theme READMEs (cd generator && bun run src/index.ts → bun run build)
• themes/neovim/README.md: update for synthpunk.nvim dedicated repo

Manual steps before first release

1. Create dev branch from main, set as default
2. Create empty slowdini/synthpunk.nvim repo
3. Set secrets: RELEASE_PR_TOKEN, VS_MARKETPLACE_TOKEN, OVSX_TOKEN, ZED_PUBLISH_TOKEN, SYNTHPUNK_NVIM_DEPLOY_KEY
4. Set repo variables: PUBLISH_VSCODE=true, PUBLISH_OPENVSX=true, PUBLISH_ZED=true, PUBLISH_NVIM=true
5. Confirm VS Code Marketplace publisher account synthpunk

Test plan

• bun run check passes (biome + tsc)
• bun test — 91 pass, 0 fail (84 original + 4 bump-version + 3 lockstep)
• bun run build + generator sync check — generated files match committed
• bun scripts/bump-version.ts 0.2.0 — bumps all 3 manifests correctly (verified, then reverted)
• First real release: trigger Release PR workflow with 0.1.0, verify end-to-end