fix(admin): entries form & schema builder UI polish, sticky toolbar, branded loader

[zeshan-rx]

Summary

Cluster of admin-side UI fixes for the Entries forms, Schema Builder, sidebar, and global permission-loading state. Most user-visible: field widths are now respected across nested groups / components / builder rows, the Schema Builder toolbar stays pinned while scrolling, the Entries table no longer shows the id column by default, the sidebar stops flashing an empty state on hydration, and PermissionGuard gets a branded glassmorphic loader.

• Fixed field width and row layout issues where grouped fields were ignoring admin.width
• Added spacer columns to preserve partial-width field sizing in rows
• Unified nested field layout behavior with top-level canvas layout logic
• Routed component and group children through shared FieldRow rendering
• Kept id in column toggler while removing it from default visible entry table columns
• Made builder toolbar sticky with correct scroll parent handling
• Fixed sidebar hydration flash by delaying menu rendering until router and permissions load
• Added branded glassmorphic permission loader with animated Nextly spinner UI
• Added ?debug_loading=true support to force-enable loading state for testing

Type of change

[X] Bug fix (non-breaking change which fixes an issue)
[X] UI / polish / refactor (no behaviour change for end users beyond visuals)

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would change existing behavior)
• Documentation update
• Refactor / chore (no user-facing change)

Related issues

Changeset

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• I added a changeset (or this PR only touches non-publishable code: docs, tests, internal tooling, apps/*)
• I selected the correct semver bump (patch / minor / major)

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Test plan

• pnpm lint
• pnpm check-types
• pnpm build
• Manually verified the change

Checklist

• I read CONTRIBUTING (if it exists)
• My commits follow the Conventional Commits spec (enforced by commitlint)
• I targeted the main branch
• I updated relevant documentation

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Notes for reviewers