Fixes hyperhive#2893: 'Element.attachShadow: Unable to re-attach to
existing ShadowDOM', crashing swarm.js's live-update render path.
A custom element's connectedCallback fires again on a same-document
*move* (insertBefore/append repositioning an already-connected node
runs the removal + insertion steps for its whole subtree), not just
on a fresh mount. swarm.js's row-fingerprint cache reuses + reorders
existing <li> subtrees on live updates -- reordering an unchanged,
cached row moves its already-initialised <hive-agent-menu>/<hive-menu>
without ever really detaching it from the document, so connectedCallback
re-runs full setup on an instance that's already set up. attachShadow()
throws unconditionally if the host already has a shadow root, and
HiveAgentMenu's unconditional child-menu creation would have appended a
second <hive-menu> on top of the first, doubling the dropdown, once the
shadow-attach crash itself was out of the way.
Both connectedCallbacks now bail early if already initialised
(shadowRoot present / _menu already built). Reproduced the crash and
duplicate-menu bug with an unguarded control copy of both files driven
via headless Chromium (simulating the exact row-reorder move), then
confirmed the guarded version throws nothing, keeps the same shadowRoot
object identity across the move, and doesn't duplicate the dropdown.
Per mara's review on #2881: the dropdown box chrome (background/border/
radius/shadow/min-width/white-space) and the trigger button's base
icon-button treatment are both reachable from hive-menu.css now --
the box chrome lives on hive-menu's own shadow-owned .menu-dropdown
wrapper (no slotting constraint at all), and the trigger button is
styled via ::slotted([slot='trigger']) since it's the top-level slotted
node for that slot. Item-row styling stays in the caller's stylesheet
-- ::slotted() only reaches directly-slotted elements, not their
descendants, so individual dropdown items are architecturally
unreachable from hive-menu's shadow tree. Verified interactively via
headless Chromium/CDP: trigger opacity/hover/border-radius and the
dropdown wrapper's background/border all resolve correctly, hover and
click-to-open still work.
<hive-agent-menu> bundled two concerns: the agent-specific trigger/item
list, and generic "click a trigger, get a positioned dropdown" mechanics
(shadow attach, open/close, singleton close-on-open coordination,
outside-click/Escape handling). Pulled the latter out into a new
@hive/shared/hive-menu.js (<hive-menu>), following the established
per-component-directory + ._opts-before-append shadow-DOM pattern
(<hive-dialog>). <hive-agent-menu> now just builds the "⋮" trigger and
the action list and hands them to an internal <hive-menu> instance.
<hive-menu> takes ownership of every <hive-menu> instance in the app for
singleton coordination (closeAllMenus, renamed from closeAllAgentMenus)
— a deliberate widening from the old per-agent-menu-only tracking, since
the mechanism was never agent-specific to begin with.
The one subtlety worth spelling out: <hive-menu> projects the caller's
opaque trigger/content nodes via named <slot>s rather than moving them
into its own shadow root. That's load-bearing, not cosmetic — if it
re-parented them into its own shadow tree instead, <hive-agent-menu>'s
own classes (.agent-menu-btn, .agent-menu-item, ...) would stop applying,
since a <style> only styles elements within the same shadow tree/document
it's part of, and only slotting (not re-parenting) keeps the caller's
nodes in the caller's own tree for styling purposes. That in turn made
<hive-agent-menu>'s own shadow root redundant once it wasn't the thing
positioning or owning open/close state anymore, so it's dropped in favor
of a plain light-DOM element styled by dashboard.css (already the one
page it renders on) — hive-agent-menu.css is gone, its rules folded into
dashboard.css's per-agent-menu section, minus the positioning rules that
moved into hive-menu.css as the new generic `.menu-dropdown` wrapper.
Verified with a standalone esbuild bundle + a cached nix chromium driven
over raw CDP (no puppeteer/playwright/python3 available): hover-reveal
opacity, dropdown open/close/positioning, outside-click/Escape dismissal,
and cross-instance singleton coordination all behave identically to
before the split.
