Queue Edit Mode changes for the agent and fix inline text editing

[jamesrochabrun]

Edit Mode had two problems, both about changes going nowhere visible.

Text was impossible to keep typing. The page bridge re-posts the selected element on every DOM mutation — including the live edit being typed — and its capture is textContent.trim(). A typed trailing space was echoed away, and with it the ability to start another word; the toolbar's own field also clipped at lineLimit(1...3) with no scroll. And proven direct writes applied silently, so a color change or a static-preview text edit could look ignored while an edit that happened to fall back to the agent was the only one that showed up in the tray.

Every change now queues. Agent-bound edits mirror into the session tray as one Edits chip per element — upsert keyed by selector, since element captures carry a fresh UUID on every DOM read, so a slider drag updates one chip instead of piling up. Reverting an edit drops the chip, removing a chip drops the batch behind it, and Send / ⌘↵ commits the element in progress and sends the whole tray (a failed send leaves it intact). Direct-to-source writes move behind the existing setting — now off by default, and it also gates the static-preview text splice.

Prompts carry the rules that were missing. A preamble leads every queued batch: change the value at its definition and never replace a var(--token) / variable / constant with a literal, add or pick a token when the definition is shared, keep the styling mechanism (Tailwind stays Tailwind, CSS modules stay CSS modules) and the value notation (unit, color form, clamp() shape), edit text where it is defined, change nothing else, and stop and explain rather than force it. Below that, a where these values live today section merges CSSOM declared values with proven project-relative files:

- font-size: declared as `clamp(1.5rem, 4vw, 3rem)` in rule `.hero-sub` (site.css) — verified in styles/site.css
- color: declared in styles/site.css

Rule proving still runs with direct writes off, because that provenance is what the section is made of. A failed direct write now downgrades into the batch keeping its original value, instead of a bare target value with no origin.

Text editing is AgentHub's own editor now (WebPreviewTextContentEditor): local draft, grows with content and scrolls instead of clipping, with a pure draft policy — the focused draft always wins, an unfocused one yields only to non-whitespace changes. refreshFromLiveElement syncs DesignToolbarValues in place rather than replacing the object, so a mutation echo no longer resets bound editors, the caret, or properties already edited. The pending-edits pill is removed; the tray says the same thing with more detail and one Send.

Tests: new draft-policy suite; queue upsert / chip labels / preamble appearing exactly once for a mixed queue; chip summaries and declaration-site lines; live read-back preserving in-flight text and toolbar state; peek-without-consume; queue-first routing for proven properties and static-preview text. The four direct-splice tests now opt into the setting so that path stays covered. Targeted AgentHubCore suites and the app build pass; the editor has not been exercised in the running UI yet.