Chart Builder: open a snippet in the builder to edit it in place

docs/architecture/03-modal-system.md

@@ -284,6 +284,13 @@ export function toggleDatasets(): void {
 }
 ```
 
+> **Pre-hydrate variant — open without `init`.** When a modal must open onto state the
+> caller already loaded (the Chart Builder's _Open in builder_ edit flow — `openChartBuilderForEdit`
+> hydrates the builder from a snippet first), the opener sets the active modal, snapshots, and
+> syncs the URL **itself** and **skips the registry `init`** — running `init` would re-derive the
+> default state and clobber the hydration. Such an opener is the exception, not the rule: ordinary
+> opens go through `openModal` so `init` is the single place transient state is seeded.
+
 ### Change detection
 
 ```ts

docs/architecture/10-interaction-and-feedback.md

@@ -495,6 +495,22 @@ call the same functions as the visible control — one code path, two doors.
 _(Consulted via /council → NN/g #6/#7, Carbon menu-buttons/overflow-menu. This bullet is
 the contract; cite it, not the source.)_
 
+**Resolved — content-gated toolbar actions hide; state-gated actions disable.** Two ways a
+toolbar action can be inapplicable, with opposite affordances. **State-gated** — applicable
+to this object in principle, just inert right now (Revert with no draft changes, Config in
+the read-only Published view) → **disabled**: the user can act (edit / switch view) and it
+lights up. **Content-gated** — inapplicable to _this spec's shape_, and nothing the user can
+do in the moment changes that (_Extract to Dataset_ needs inline data; _Open in builder_
+needs a builder-representable spec referencing an existing dataset) → **hidden**. A
+permanently-disabled control the user cannot enable reads as broken or teasing, not as
+guidance (NN/g #6 — a disabled state must imply "do X and this becomes available"; Carbon
+button states). So _Open in builder_ (spec §06) sits in the editor toolbar beside _Extract
+to Dataset_ and follows its visibility — present only when the active snippet round-trips
+through the builder and its dataset exists. This refines "disabled is for temporarily
+unavailable actions" (below) from the unbuilt-feature case to the per-spec case.
+_(Consulted via /council → NN/g #4/#6, Carbon button usage/states. This bullet is the
+contract; cite it, not the source.)_
+
 **Resolved — field→channel assignment: explicit choice, visible armed state.** Clicking a
 shelf field with no channel armed opens an explicit **channel chooser** (the channels that
 accept the field; an occupied one is labelled with what it replaces) — never a silent