Adds client/pnpm-workspace.yaml so that pnpm install from client/
resolves galaxy-api-client as a workspace member. The per-package
client/packages/api-client/pnpm-lock.yaml goes away in favor of the
single client/pnpm-lock.yaml covering the whole workspace.

CI is simplified to a single install step, then workspace-filtered
build/test/publish invocations (pnpm --filter @galaxyproject/galaxy-api-client).

This is the first real workspace member; the packages/* glob is ready
to accept extractions (galaxy-utils, galaxy-ui, galaxy-composables) in
follow-up PRs.

With the workspace in place, flip the client<->api-client relationship.
The OpenAPI schema becomes canonical in the api-client package, and the
main client re-exports its types from @galaxyproject/galaxy-api-client
as a workspace dependency. The old symlink from api-client back into
client/src/api goes away -- the library no longer reaches into the app.

Changes:
- Move client/src/api/schema/schema.ts (48K lines) into
  client/packages/api-client/src/schema/schema.ts as the canonical copy.
- Add client/packages/api-client/src/schema/index.ts matching the old
  barrel.
- Update api-client's api-types.ts to import from the new local path;
  remove the no-longer-needed client/packages/api-client/src/api symlink.
- Replace client/src/api/schema/index.ts with a re-export from
  @galaxyproject/galaxy-api-client.
- Add @galaxyproject/galaxy-api-client as a workspace:* dep in client.
- Wire a postinstall hook in client/package.json to build api-client on
  pnpm install so its .d.ts is available to vue-tsc.
- Update make update-client-api-schema to generate into the new canonical
  location.
- Fix the one file still importing from @/api/schema/schema (the index
  barrel re-exports components already).

This PR now demonstrates the workspace end-to-end: a real library
package, consumed by the app, building through the workspace toolchain.
Further extractions (galaxy-utils, galaxy-ui, galaxy-composables) follow
in subsequent PRs using the same pattern.

During make client-dev-server, imports of @galaxyproject/galaxy-api-client
now resolve directly to packages/api-client/src/index.ts rather than its
built dist/. Edits to the package source trigger HMR in the main client
without a manual rebuild.

Production vite build is unchanged -- it still consumes the package via
its package.json exports (dist/index.js + dist/index.d.ts), so the built
bundle reflects the same interface external consumers would see.

defineConfig switches to a function form so 'command' is available for
the dev/build discriminator. Only the resolve.alias field is
command-dependent; everything else is shared.

Adds client/packages/README.md covering what lives there, the bar for
adding new packages, and common ops (pnpm --filter, postinstall, the
dev-mode source alias). Cross-links from client/README.md so the main
client docs point at it.

The client/ package.json now has @galaxyproject/galaxy-api-client at
workspace:* and a postinstall that filters into the workspace to build
it. npm publish doesn't rewrite the workspace: protocol, so the published
tarball would carry the literal "workspace:*" and break downstream
installs; pnpm publish substitutes the real version. The postinstall is
also workspace-only -- if it ships in the tarball, consumers' npm install
fails when pnpm --filter runs outside any workspace -- so npm pkg delete
strips it before pnpm publish runs.

ColorVariant lives with the other component variant types inside
BaseComponents/ so G-components don't need to reach back into
@/components/Common to get their own types. Common/index.ts re-exports
for the app-code consumers that still import it from there.

Prep work for carving BaseComponents into a @galaxyproject/galaxy-ui
workspace package -- the package needs its types self-contained.

Drops the @import of @/style/scss/theme/blue.scss and switches to the
--color-* tokens from custom_theme_variables.scss (PR galaxyproject#19946, Laila
Los): --color-blue-600 for info, --color-orange-600/200 for warning,
--color-green-600/200 for success, --color-red-600/200 for danger, and
--color-grey-100 for neutral background.

GTip was the only G-component with an explicit theme SCSS import, so
removing it cleans up the last bit of mandatory theme coupling in
BaseComponents. The SCSS scale-color() calls for warning/success/danger
backgrounds map to the 200-shade of each hue, which is the closest
pre-defined match and avoids the partial-transparency pattern the color
system intentionally moved away from.

Prep work for the @galaxyproject/galaxy-ui workspace package: the
package can't depend on Galaxy's SCSS theme, so it consumes CSS custom
properties injected by the app at :root.

GHeading is a near-identical variant of Common/Heading.vue with the
Galaxy-specific bits removed: no IconLike dependency from
@/components/icons/galaxyIcons (accepts FontAwesome IconDefinition
directly), and no @import of the Galaxy theme SCSS -- the separator
stripe uses var(--color-grey-200) instead of $brand-secondary (same
hex value).

GModal was the only G-component importing Common/Heading.vue. It now
uses GHeading, which keeps BaseComponents self-contained. Heading.vue
stays in place for the dozens of feature-component consumers.

Prep work for the @galaxyproject/galaxy-ui workspace package: the
package can't depend on Galaxy-specific icon types or theme SCSS.

GModal's match() call just maps small/medium/large to sm/md/lg for
GHeading -- swap it for a plain record lookup. GForm's assertDefined
on the form template ref becomes an inline null check. Both are prep
for the galaxy-ui extraction: neither helper is UI-shaped, so those
stay put in @/utils/ while the component boundary stays clean.

Adds packages/ui/ as a second workspace member alongside api-client --
private, source-only, no library build. Empty src/index.ts barrel;
components and composables move in next.

Wires galaxy-ui into the main client as a workspace:* dep and as an
unconditional resolve.alias in vite.config.mjs (serve and build). The
api-client alias stays serve-only because it has a real dist/ build
and production consumes that via package.json exports; galaxy-ui is
internal-only so we skip the build step entirely and let the main
client's @vitejs/plugin-vue2 handle the Vue 2 SFCs from source in
both dev and prod.

client/packages/README.md now lists both packages and calls out the
"flips to a library build + publish when the interface stabilizes on
Vue 3" intent.

Relocates 15 G-prefixed base components (GButton, GButtonGroup, GCheckbox,
GCollapse, GHeading, GLink, GModal, GOverlay, GTab, GTabs, GTip, GTooltip,
Form/{GForm,GFormInput,GFormLabel}), 6 supporting composables
(accessibleHover, clickableElement, currentTitle, markdown, resolveElement,
uid), componentVariants, and tooltipTiming into packages/ui/src/. Old
paths become re-export shims so consumers keep working unchanged --
app-side imports get updated gradually rather than in a mass codemod.

Internal imports within the package are rewritten to relative paths; zero
@/ imports remain in packages/ui/src/, so the boundary doesn't silently
depend on the main client's source tree.

galaxy-ui is "private": true and never gets published to npm. With it
declared as a runtime dependency, pnpm publish would rewrite workspace:*
to 0.0.0-internal in the published galaxy-client tarball, and consumers'
npm install would then fail trying to fetch a non-existent package.
galaxy-ui is a source dep only -- its compiled output is bundled into
client/dist/ at build time, so consumers don't need it at install time.