docs: changelog Unreleased section for tonight's Studio work

Channel switcher, prominent bilingual store manager + suggested stores
+ pinned-key field, approval payload clarity, copyable errors, filter
crash fix, welcome grid, pulsing dot.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

CHANGELOG.md

@@ -3,6 +3,40 @@
 All notable changes to `chain_studio` recorded here. Pubspec
 version + `kStudioVersion` in `lib/main.dart` stay in lockstep.
 
+## Unreleased
+
+### Added
+
+- **Channel switcher in the sidebar.** The active-channel pill (and the
+  collapsed chip) is now click-to-switch: a menu of every channel with
+  its running state + a check on the active one; switching writes
+  `~/.chain/current-channel`, restarts that channel's daemon, and Studio
+  repoints to it.
+- **Module-store manager is prominent + bilingual.** The store page
+  gains a labelled "Add store" button (was a bare icon) opening a fully
+  localized dialog: configured stores, a curated **Suggested stores**
+  shelf with one-click add/remove (probed for reachability — shows "not
+  available yet" until a store's index is published), and an optional
+  per-store **pinned public key** field.
+- **Approval payload clarity.** The approval card always shows the
+  payload section: a present payload scrolls inside a height-capped
+  copyable box; an absent one explains that the flow's approval step
+  chooses what to surface via its `show:` field.
+
+### Fixed
+
+- **Errors are copyable everywhere.** System-AI test-connection, the
+  Settings dialog, and the Audit status bar rendered failures as
+  non-copyable text; all now route through `ChainErrorBox` /
+  `SelectableText`.
+- **Filter dialog crash** on the store page — a `Spacer` inside
+  `AlertDialog.actions` (an `OverflowBar`, not a Flex) threw; the
+  buttons now sit in a `Row`.
+- **Welcome docs grid** tidied into equal-height paired rows.
+- **Approval card** leads with the human prompt; the `flow › step` id is
+  demoted to a metadata line.
+- **Pulsing sidebar connection dot** restored when connected.
+
 ## 0.70.0 — 2026-06-13
 
 ### Added