render: open Modal content on trigger activation

[joestump]

What

Closes the "Modal renders only its trigger" gap: modals now open on Enter and close on Esc, with the content child rendered as a bordered in-flow block (a true overlay is out of scope for a string-rendered surface — in-flow expansion is the honest terminal equivalent).

How

• Focus ring (render/render.go): a Modal joins the ring as a single focusable drawn as its trigger — the trigger subtree is the modal's chrome (like a button's label) and never joins separately. Content focusables join only while the modal is open, matching what is on screen.
• Open/close state (render/modal.go, new): open modals are tracked as a stack in open order, so Esc closes the innermost of nested modals first. toggleModal/closeTopModal re-derive the ring and keep focus on the modal (so Esc returns focus to the trigger).
• Rendering (render/containers.go): closed = cued trigger only (▹ idle / ▸ focused, the TextField glyph-swap convention — chrome stays monochrome). Open = trigger + content in the CardBorder box with renderCard's width budgeting; the border is kept even in compact mode since it is the only signifier separating modal content from the flow.
• Apply merges (render/composite.go): open state survives updateComponents (pruned only when a component stops being a modal) and is cleared by deleteSurface.
• Standalone esc interplay (a2tea.go): new HasOpenModal probe mirroring EditingText — an open modal consumes Esc before Standalone's esc-quit; Ctrl+C remains an unconditional quit.

Tests

• render/modal_test.go (new): closed renders trigger-only; modal is the sole focusable (trigger buttons excluded); focus-cue glyph swap; Enter opens (bordered content, content button joins ring); Enter toggles closed; Esc closes with focus inside content and restores focus to the modal; Esc no-op with nothing open; open state preserved across Apply; open state pruned when the modal is replaced; nested modals close innermost-first.
• a2tea_modal_test.go (new): Standalone Esc closes the open modal without quitting, then quits once closed; Ctrl+C quits even with an open modal.
• Removed the obsolete hidden-content-note placeholder test; go build ./... && go vet ./... && go test ./... green locally.

Docs: docs/wire-format.md and README.md "Not yet" lists updated. The website/ docs site is deliberately untouched — deferred to the post-merge docs pass.

Fixes #46

🤖 Posted on behalf of @joestump by Claude.

[joestump]

Adversarial review against the #46 contract. Verified locally: go build ./... && go vet ./... && go test ./... green on the PR head (1a4a96c).

What I verified

• Ticket Done-when: trigger opens content (Enter), Esc closes, Standalone still quits when no modal is open, open state preserved across Apply, docs "Not yet" lists updated (README + docs/wire-format.md; website/ correctly deferred).
• State preservation: applyComponents prunes before re-collecting focusables (render/composite.go:80-82), so a replaced modal can't leak content focusables into the ring; deleteSurface clears openModals; focus preservation across merges works for modals since it keys off the generic focusables[focusIdx].
• Key routing: Enter checks focusedIsModal before focusedIsButton (render/render.go:245), so a focused TextField or button inside open content behaves exactly as before; Esc has no text-editing semantics to steal; q-while-editing and unconditional Ctrl+C both covered by tests.
• Guards: focusedComponent zero-value on empty ring, closeTopModal empty-stack no-op, missing trigger/content IDs fall through to the existing [a2tea: missing component] path, cycle guard covers modal content in both render and focus walks.
• Tests assert behavior (rendered content, ring composition, focus restore, quit commands), not just execution. Good coverage.

Blockers

None.

Nits

1. Phantom nested-modal open state (render/modal.go toggleModal/HasOpenModal). Enter-toggling an outer modal closed while an inner modal (inside its content) is still open leaves the inner ID in openModals. Verified with a runtime probe: HasOpenModal() returns true while the view shows no open modal, so in Standalone the next Esc is silently swallowed (it pops the invisible inner entry) and the user needs a second Esc to quit. pruneOpenModals doesn't catch this — the inner component is still a modal, just unreachable. Suggested fix: after any close/toggle, drop open entries not reachable from the root through open content (a reachability variant of pruneOpenModals), or make HasOpenModal count only reachable entries. Edge case (nested modals + Enter-toggle of the outer instead of Esc), self-corrects on the extra Esc — not blocking.

2. Trigger cue overflows the width budget by 2 cells (render/containers.go:131). The trigger child renders under the full s.width budget and then gets the 2-cell "▹ " prefix, so an exact-width trigger line lands at width+2; continuation lines of a multi-line trigger also aren't indented under the cue. TextField wraps cue+value to s.width (render/fields.go:72) — mirroring that (render trigger under s.width-2, indent continuations like bullet) would keep the convention consistent. Cosmetic.

3. Stale comment (render/composite.go:71): "Remember which button held focus" — the ring now also holds text fields and modals.

Approving direction: nit 1 is worth a follow-up ticket if not fixed here; nits 2-3 are take-or-leave.

🤖 Posted on behalf of @joestump by Claude.