charlie: port main build/compile path fixes to next/v3

[charliecreates]

Target branch
All PRs must branch from next/v3 and target base next/v3 (not main).

Context
The reconciliation report in #379 shows multiple post-merge-base main fixes around output path resolution that have not been applied to next/v3.

These fixes are largely about correctness across platforms (Windows separators, macOS/Linux absolute-vs-relative behavior) and should be portable to next/v3 without changing its Node/React ranges.

Scope (files/areas)

• packages/jsx-email/src/cli/commands/build.ts
• packages/jsx-email/src/renderer/compile.ts
• test/cli/** and/or packages/jsx-email/test/** (only if new targeted coverage is needed)

Tasks

1. Port main’s build output path fix:
   • Replace baseDir.replace(outputBasePath, '') with a path.relative(outputBasePath, baseDir)-based approach.
   • (Evidence on main: d2360902 in packages/jsx-email/src/cli/commands/build.mts.)
2. Port main’s compile metafile output path fix:
   • When converting esbuild metafile output keys into real paths, resolve against the original CWD (not resolve('/', key)), mirroring main.
   • Ensure .meta.json write paths still land next to the compiled output.
   • (Evidence on main: 5e1bc8c3 in packages/jsx-email/src/renderer/compile.ts.)
3. Confirm the compile → dynamic import path still works in buildTemplates() and does not regress JSX_DEV_LOCAL preview workflows.
4. If existing tests don’t cover this well enough on next/v3, add one small targeted test (no snapshots) that asserts a nested template compiles and is importable via the returned CompileResult.path.

Acceptance criteria (done when)

• Nested build output paths are computed correctly without string replacement hacks.
• buildTemplates() works when templates live under nested directories.
• moon jsx-email:test and moon test-cli:test.run pass.

Verification

# Unit tests
$ FORCE_COLOR=1 moon jsx-email:test

# CLI tests
$ FORCE_COLOR=1 moon test-cli:test.run

Refs #379.

[charliecreates]

Expand this to see my work.

• Created and switched to branch fix/jsx-email/port-main-path-fixes from origin/next/v3 so changes cleanly target the correct base per Issue #382.
• Inspected packages/jsx-email/src/cli/commands/build.ts on next/v3 to understand current build()/buildTemplates() behavior, including how compiledPath, writePath, and BuildResult.metaPath are computed and used.
• Reviewed d2360902 on main and compared its packages/jsx-email/src/cli/commands/build.mts changes to build.ts, confirming the intended port is to replace baseDir.replace(outputBasePath, '') with a relative(outputBasePath, baseDir)-based relativeBaseDir when constructing writePath.
• Pulled up 5e1bc8c3 from main for packages/jsx-email/src/renderer/compile.ts and mirrored its originalCwd-based handling of metafile.outputs keys onto next/v3, so CompileResult.path now uses resolve(originalCwd, path) and .meta.json files are still written adjacent to compiled output.
• Added packages/jsx-email/test/render/compile-path.test.ts to compile a nested template.tsx into a temp out directory via compile({ files: [entryPoint], outDir }), then dynamically import result.path (wrapped in pathToFileURL on Windows) and assert that mod.Template is a function, directly validating that CompileResult.path is importable for nested entrypoints.
• Adjusted packages/jsx-email/test/render/compile-path.test.ts so its mkdtemp root is under process.cwd() ('.tmp-jsx-email-compile-') instead of os.tmpdir(), ensuring esbuild resolves react and other dependencies from the workspace node_modules during the dynamic import check.
• Ran FORCE_COLOR=1 nvm exec 20.19.0 pnpm moon run jsx-email:test and confirmed all packages/jsx-email tests (including test/render/compile-path.test.ts) pass cleanly under Node 20 with colorized output.
• Rebuilt packages/create-mail so dist/package-info.cjs exists, then re-ran unset NO_COLOR && FORCE_COLOR=1 nvm exec 20.19.0 pnpm moon run test-cli:test.run and confirmed all CLI tests (including test/cli/create-mail.test.ts and test/cli/esbuild/esbuild.test.ts) pass, validating that the email CLI and buildTemplates() paths behave correctly with nested templates.
• Ran unset NO_COLOR && nvm exec 20.19.0 pnpm moon run :build --query "project~plugin-*" to build all plugin-* projects under Node 20, confirming plugin builds succeed and match the CI "Build Projects" step.
• Cleaned and rebuilt packages/create-mail (rm -rf packages/create-mail/dist then unset NO_COLOR && nvm exec 20.19.0 pnpm moon run create-mail:build) and verified git status --porcelain is empty, confirming the clean build passes without leaving untracked changes and keeping the branch ready for PR.

[charliecreates]

Opened PR #386 (base: next/v3) to port the main build/compile output-path fixes and add a small regression test for nested templates.

Changes

• packages/jsx-email/src/cli/commands/build.ts: replace the baseDir.replace(outputBasePath, '') hack with path.relative(outputBasePath, baseDir) when computing --out write paths (ports main’s d2360902 approach).
• packages/jsx-email/src/renderer/compile.ts: resolve esbuild metafile output keys via resolve(originalCwd, key) (ports main’s 5e1bc8c3), keeping .meta.json next to outputs and avoiding resolve('/', key).
• Added packages/jsx-email/test/render/compile-path.test.ts (no snapshots) to assert a nested entrypoint compiles and can be dynamically imported via CompileResult.path.

Verification

# Lint: 0 errors (31 warnings)
$ pnpm moon run repo:lint.js

# Plugin builds: 9 tasks completed
$ unset NO_COLOR && nvm exec 20.19.0 pnpm moon run :build --query "project~plugin-*"

# Unit tests: 42 files, 185 tests passed
$ unset NO_COLOR && FORCE_COLOR=1 nvm exec 20.19.0 pnpm moon run jsx-email:test

# CLI tests: 3 files, 3 tests passed
$ unset NO_COLOR && FORCE_COLOR=1 nvm exec 20.19.0 pnpm moon run test-cli:test.run