feat: dgbuild new-skein / open-skein — interactive Skein UI without VS Code

[hlship]

What

Two new dgbuild commands that run the full interactive Skein UI — transcript, nav graph, trace panel, keyboard shortcuts — from a plain browser, with no VS Code:

• dgbuild new-skein [name] — create a skein (default default), refuse to overwrite an existing one
• dgbuild open-skein [name] — open an existing one, refuse a missing/non-dgdebug skein, replay every branch on load (same as the extension)

Both stand up the existing SkeinService on localhost, print the URL, open a browser (--no-open to skip), and block until the in-UI Quit button or Ctrl+C. Options: --seed (new only), --port, --theme <light|dark>, -p/--project, -v/--verbose. dgdebug only for now.

How

SkeinService already serves every interactive route — this reuses it wholesale via a headless host (src/cli/commands/skein-server.ts), the counterpart of extension.ts's wiring. No logic duplicated.

• ServiceConfig gains standalone + onQuit; both threaded through SessionDisplayInfo so the extension's rendered output is byte-identical (everything is gated off when standalone is unset)
• Dirty tracking: reference-identity check against the tree at last save (SkeinTree is immutable-persistent) — O(1), all in service.ts
• Quit / orderly shutdown: POST /actions/quit → if dirty, broadcast sk.showQuitModal() (Save and Quit / Quit Without Saving / Cancel); otherwise broadcast a "you may close this window" screen to the transcript and any open /trace tab, then fire onQuit. Ctrl+C also tears down cleanly (warns, can't save). beforeunload guards an accidental tab close.
• Trace opens in a second browser tab (named window, reused/refocused). window.open runs in the Trace button's own data-on:click — the menu popover's data-on:click__stop swallows the event before a document listener would see it. Row click-to-open-source is a no-op here (no editor); hover preview still works.
• Fix (pre-existing bug): trace-tree indentation compounded quadratically — renderRow scaled margin-left by dgdebug's raw stack depth on an element that's already nested in its parent's. Now one fixed CSS step per level on .trace-children.

Tests

• new-skein.spec.ts / open-skein.spec.ts — option parsing + create/open guards
• skein-server-integration.spec.ts — real dgdebug: standalone page, send-command → dirty → showQuitModal, save → clean → showShutdownScreen, open replays clean, self-skips without the toolchain
• extended render.spec.ts / traceRender.spec.ts / knot-menu.spec.ts
• Full suite: 973 passing, tsc clean

Verified end-to-end against sanddancer-dialog (554-knot skein) in Chrome

open-skein loads clean, navbar shows the Quit button, Trace opens/refocuses one /trace tab that live-updates, the indentation fix renders a tight staircase, Ctrl+C shuts down with no orphan dgdebug.

🤖 Generated with Claude Code