fix(web): ResourceControls single-scroll, full-height panel, right/down chevrons (#1462) (#1464)

* fix(web): ResourceControls single-scroll + right/down disclosure chevrons (#1462)

Two fixes to the Resources controls panel:

1. Sections scrolled prematurely. `panelMaxHeight` divided the available
   height equally across open sections (`… / n`), so a section with many
   items scrolled while sparse siblings left their equal share unused.
   Replace the per-section ScrollAreas with a single viewport-bounded
   ScrollArea.Autosize around the whole accordion (matching ToolControls /
   PromptControls). Sections size to content; nothing scrolls until the
   open sections' combined height exceeds the cap.

2. Accordion chevrons pointed down/up. Add a `disclosure` Accordion theme
   variant + `.disclosure-chevron[data-rotate]` rule that rotates a
   right-pointing RiArrowRightSLine 90° (not Mantine's default 180°), so
   closed sections point right and open sections point down — matching the
   ResourceLink chevron convention.

Also keep empty (disabled) sections out of the accordion's open set so
they render collapsed with a right chevron instead of an open-but-empty
panel. Verified all states in a real browser via Playwright.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test(web): cover empty-section-collapsed behavior in ResourceControls (#1462)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(web): make Resources sidebar fill panel height before scrolling (#1462)

The first pass capped the accordion scroll region at a fixed sub-viewport
height (`100vh - … - 160px`), so the sidebar scrolled before reaching the
height of the detail panel to its right.

Make the sidebar card full-height instead: add a `sidebar` Card variant
(height:100%, flex column, overflow hidden), give it `flex: 1`, and let
ResourceControls' root Stack (`flex: 1; min-height: 0`) and a plain
flex-filling ScrollArea claim the space below the title/search. The card
now matches the detail panel's height exactly and the single inner scroll
region scrolls only once the open sections overflow the full panel.

Adds a ResourcesScreen ManyResources story asserting the sidebar/detail
height match and that overflow scrolls, plus a unit test for the
empty-section-collapsed behavior. Verified heights + scroll in a real
browser via Playwright.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(web): pin Resources section headers, scroll each section in place (#1462)

The previous pass scrolled the whole accordion as one block (headers
scrolled away). Restore pinned headers with per-section scrolling, without
the original equal-division premature-scroll bug.

The `disclosure` Accordion now fills its full-height card as a flex column
(`disclosure-sections`): controls are pinned, and each open section's panel
scrolls within its own share of the remaining height. Per-item `flex`
weights (shrink ∝ item count, grow 0) hand space from long sections to
short ones, so nothing scrolls until the combined content overflows the
panel — a long URIs list scrolls in place while Templates stays fully
visible below it. Drops the single outer ScrollArea (and useScrollMemory).

Verified in a real browser: 6 URIs → no scroll, headers pinned, empty
space at the bottom; 40 URIs → URIs panel scrolls in place, Templates
intact, all three headers pinned, sidebar still matches the detail height.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(web): Resources sidebar grows with content, capped at screen (#1462)

The `sidebar` Card variant forced `height: 100%`, so the panel was always
full-height with empty space below short content. Switch to
`max-height: 100%` (and drop `flex: 1`) so the card hugs its content and
only caps at the screen height — matching the Tools panel. When content
overflows the cap, the flex accordion still takes over per-section
scrolling with pinned headers.

Verified in a real browser: 6 URIs → card hugs (638px, shorter than the
detail panel); 40 URIs → card caps at the screen (949px == detail),
headers pinned, URIs scrolls in place.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(web): preserve empty-section intent + kill accordion collapse jump (#1464 review)

Address review feedback on PR #1464:

- Intent loss (review #1): the accordion's `value` is the filtered
  `visibleOpenSections`, so Mantine's toggle dropped open-but-empty
  sections from the persisted intent. Merge them back in the onChange
  handler so an open empty section stays open and reappears with items.
  Adds a unit test.
- Collapse animation jump (review #3): Mantine's Collapse briefly set the
  panel to its full natural height (fighting the flex layout) on
  open/close, flashing siblings. Set `transitionDuration={0}` so flex
  controls the height; restore a smooth chevron rotation via CSS. Verified
  no jump in a real browser (panel 501→0, no spike). Since closed sections
  now render no content, drop the redundant (and incorrect) "Templates"
  toggle clicks from 4 ResourcesScreen tests (the section is open by
  default) and add a section-toggle test to keep the openSections handler
  covered.
- Nits: scope the stories' chevron query to the accordion root; tighten
  the Collapsed assertion to the identity transform.

Native-vs-styled scrollbar (review #4) split out as #1466.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs(web): clarify chevron-timing and intent-merge invariants (#1464 review)

Address the two optional doc nits from the re-review:
- Note that the chevron's 200ms restates Mantine's default accordion
  duration (keep in sync if accordion timing is themed).
- Note that the unconditional empty-section merge is safe because
  empty-section controls are disabled, so `next` never contains one.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/web/src/theme/Accordion.ts

@@ -0,0 +1,17 @@
+import { Accordion } from "@mantine/core";
+
+export const ThemeAccordion = Accordion.extend({
+  // The `disclosure` variant drives two behaviours via App.css (see #1462):
+  //   - `disclosure-chevron` on the chevron slot rotates a right-pointing arrow
+  //     90° (right → down) on open, instead of Mantine's default 180° flip.
+  //   - `disclosure-sections` on the root makes the accordion a full-height
+  //     flex column: section headers stay pinned and each open section's panel
+  //     scrolls within its own (item-count-weighted) share of the space, so
+  //     nothing scrolls until the panel is full.
+  // Pair it with `chevron={<RiArrowRightSLine />}` and per-item `flex` weights.
+  classNames: (_theme, props) => {
+    if (props.variant === "disclosure")
+      return { root: "disclosure-sections", chevron: "disclosure-chevron" };
+    return {};
+  },
+});

clients/web/src/theme/Card.ts

@@ -20,6 +20,23 @@ export const ThemeCard = Card.extend({
         },
       };
     }
+    if (props.variant === "sidebar") {
+      // Sidebar container that grows with its content but never taller than the
+      // screen's available area (`max-height: 100%` of the full-height column
+      // wrapper) — like the Tools panel. Lays its content out as a column and
+      // hides overflow so that, once capped, the flex accordion below the fixed
+      // title/search takes over per-section scrolling rather than the card
+      // bleeding past the viewport (#1462).
+      return {
+        root: {
+          backgroundColor: "var(--inspector-surface-card)",
+          maxHeight: "100%",
+          display: "flex",
+          flexDirection: "column",
+          overflow: "hidden",
+        },
+      };
+    }
     if (props.variant === "preview") {
       // Container for the resource preview / template form panels: sizes to
       // content (no forced height) but caps at the screen's available area

clients/web/src/theme/index.ts

@@ -1,3 +1,4 @@
+export { ThemeAccordion } from "./Accordion";
 export { ThemeActionIcon } from "./ActionIcon";
 export { ThemeAlert } from "./Alert";
 export { ThemeAppShell } from "./AppShell";

clients/web/src/theme/theme.ts

@@ -1,5 +1,6 @@
 import { createTheme, type MantineColorsTuple } from "@mantine/core";
 import {
+  ThemeAccordion,
   ThemeActionIcon,
   ThemeAlert,
   ThemeAppShell,
@@ -56,6 +57,7 @@ export const theme = createTheme({
 
   /* ── Component overrides ────────────────────────────────── */
   components: {
+    Accordion: ThemeAccordion,
     ActionIcon: ThemeActionIcon,
     Alert: ThemeAlert,
     AppShell: ThemeAppShell,