feat: add dgbuild bundle command

[hlship]

What

Adds a bundle subcommand to the dgbuild headless CLI:

dgbuild bundle [export-name]

It builds a complete web page (out/web/ plus a zip at out/<name>-<release>.zip) for one of dialog.json's named export configurations — the command-line equivalent of the extension's Export Web Page.... This lets a GitHub Action build and publish a project release with no extension host.

How

• Wraps the existing, already vscode-free bundleWebExport pipeline (src/dialog-web-export.ts) — no core logic duplicated, no new runtime dependencies, no package.json files-allowlist changes (resources/**/* and yazl already ship to npm).
• Config selection mirrors the extension's QuickPick, resolved from a CLI arg: explicit name must match exactly; an omitted name auto-selects the sole configuration when exactly one is defined, otherwise errors listing the names.
• Preflights dialogc / dgdebug / aambundle; -v/--verbose un-quiets the dgdebug lifecycle logging from the story-info query (same pattern as run-skein).
• Any failure (missing config, missing binary, pipeline step) exits non-zero with a message.

Tests

• bundle.spec.ts — resolveExportConfig cases + validation (no dialog.json, no exports).
• bundle-integration.spec.ts — real end-to-end against dialogc/dgdebug/aambundle, self-skipping when the toolchain is absent (matches run-skein-integration.spec.ts).
• Full suite green (951 pass, 5 skipped). Manually verified end-to-end against the dgsample fixture.

Docs

CHANGELOG.md, README.md, and the command-line-dgbuild manual page (new section + a GitHub Pages CI snippet).

🤖 Generated with Claude Code