feat(dialog): the browser Forward reopens what Back closed

[ivanbanov]

What

closeOnBack becomes symmetric: the browser's Back closes the dialog (as before), and the browser's Forward now reopens what Back closed — guarded again for the next Back. No new setting: back-close and forward-reopen are one behavior (the dialog's openness tracking the history position), so the existing closeOnBack gates both.

The reopen follows the shared dismissal contract: a new onForwardNavigation callback fires first and preventDefault() vetoes; a controlled dialog only records the intent.

How

The model that keeps this cheap: the guard entry a Back press pops isn't gone — it survives in the browser's forward stack, still marking the dialog's open ground. A traversal re-entering it is the host's Forward.

• @dunky.dev/dom-navigation — interceptBackNavigation(onBack, onForward?) grew the optional second callback. A Back-closed guard parks instead of dropping; a popstate landing on its spent entry offers the reopen and re-arms the guard on the entry in place (no new entry planted). The safety invariant: parked entries always sit above every armed entry (every planted entry truncates the forward stack), so ownership of the landing entry — not traversal direction, which popstate doesn't carry — decides reopen vs unwind. Marked ground with no armed owner never unwinds a layer; without that, Forward onto a dead nested-dialog entry would wrongly close its parent. Callers that don't pass onForward behave exactly as before.
• @dunky.dev/dialog — history.forward mirrors history.back, gated by the same closeOnBack, reachable from closed and from the animated closing state (Forward interrupts the exit). The connect gains forwardNavigate(), sharing the synthesized veto payload with backNavigate().
• @dunky.dev/react-dialog — one registration spans the whole episode: armed while open, parked through a Back-close (releasing there would end the Forward watch), released on any other close or on unmount. Reopening through the trigger plants a fresh entry, truncating the spent one — exactly like navigating after a Back.

Caveats (spec'd)

• A controlled dialog's Back-close is completed by the consumer rather than by the press itself, so its entry is consumed and Forward has nothing to re-enter (URL-held open state remains the answer there, per the navigation SPEC's Reload section).
• The Forward watch lives in script, so it doesn't survive a reload.
• The Vue binding keeps today's Back-only behavior for now (it passes no onForward); noted next to the react story. Mirroring it is a small follow-up once feat(vue): the Vue substrate, opening with Dialog #38 lands.

Testing

• 13 new behavior tests: 5 dom-navigation (reopen + re-arm, decline keeps watching, release ends the watch, a planted entry truncates the watch, stacked guards reopen one per Forward lowest-first), 4 core machine/connect, 4 react (Forward reopens guarded again, no reopen after other closes, veto, trigger-reopen truncates).
• Full suite, typecheck, lint, and format pass; the closeOnBack story gained a "Simulate browser Forward" button.

🤖 Generated with Claude Code