feat: add Dashboard navigation as presentation configuration

Phase 6D pass 1. The shell's navigation was a flat list of module ids, which
is not a usable experience — and the obvious fix carries an obvious trap.
Letting a module declare its folder, or modelling "Media" as something
Livestream and Video belong to, turns a rendering preference into
architecture: a folder becomes an owner, membership starts to look like a
dependency, and the flat module graph acquires a hierarchy nobody decided on.

So the rule comes first: a Dashboard group is a label on a rendering bucket.
No manifest, no version, no artifact, no API, no lifecycle; nothing depends on
it. Livestream depends on Video because it calls Video's functionality, and
that orders startup. Livestream is shown under Media, and that orders nothing.
No parent module, child module, owning module, or group-derived dependency
appears anywhere in the contracts.

No manifest change and no version 5. `manifest.name` has been required since
version 1 and already is the module's product identity, so the shell renders
"Livestream" instead of `livestream` with nothing added. `suggestedGroup` is
deliberately deferred rather than shipped: it would force a hard
manifest-version cutover for a hint, and its only correct semantics needs
initialization logic that risks a suggestion overwriting an administrator's
decision. Defaulting and ownership are different things.

Two Core tables (migration 0003) hold groups and placements — server-side,
because a church configures its Dashboard rather than one browser;
platform-global, because no organization model exists to scope them to.
`group_id` is `on delete set null`, so deleting a group ungroups its modules
and a dangling reference is impossible. `module_id` carries no foreign key,
because modules are packages rather than rows, so a placement for an
uninstalled module is retained and restores its position on reinstall.

`resolveDashboardNavigation` is a pure function of configuration plus the
mountable set: an unplaced module is ungrouped and visible with no
initialization write, an absent module renders nothing, empty groups are kept,
and ordering is total with the module id as final tie-break.

`GET /api/v1/dashboard/navigation` returns the resolved view, layered on top of
the host-neutral module UI inventory rather than merged into it — each generic
descriptor is embedded untouched, so a standalone host never inherits Dashboard
semantics. Reading needs the permission the inventory already needs; organizing
needs the new platform permission `core.dashboard.navigation.manage` through a
narrow, idempotent, closed-validation mutation contract. No editor UI.

The flatness rule is executable: a test discovers real fixtures with a genuine
dependency, arranges them four ways including both in one folder and the
dependency inverted in presentation, and asserts discovery order, dependency
declarations, and the module set stay byte-identical. The end-to-end test
organizes a real installation through the real API, mounts a module from inside
a group, moves it, and asserts the navigation entry is byte-identical across the
move and still mounts the same artifact.

The shell's client for the generic inventory became dead code and was removed
rather than kept speculatively; the endpoint itself is unchanged.

Co-Authored-By: Claude Opus 5 <[email protected]>

docs/architecture/platform-architecture.md

@@ -267,9 +267,40 @@ checked to contain exactly one dynamic import with no module identity baked in.
 from Core's own evaluator and stay presentation-only — server authorization is proven unchanged by a
 test in which a UI holding no grant calls its API anyway and is refused.
 
-**This is not the Dashboard.** No navigation, grouping, icons, ordering, design system, or routing;
-the selector lists module ids. A production CSP and a deployment for the built shell, sign-in UI,
-general asset publication, and the standalone host remain future work.
+**Phase 6D pass 1 adds the Dashboard navigation model, and fixes the rule it could have broken.**
+[ADR 0027](decisions/0027-dashboard-navigation-and-flat-modules.md) establishes that a Dashboard
+group is **presentation configuration and never module structure**. A group is a label on a rendering
+bucket: no manifest, version, artifact, API, permission, or lifecycle, and nothing depends on it.
+Placing two modules in one folder creates no relationship between them; *Livestream depends on Video
+because it calls Video's functionality* orders startup, while *Livestream is shown under Media*
+orders nothing. Modules stay flat, with no parent, child, owner, or group-derived dependency.
+
+No manifest change was needed: `manifest.name` has been required since version 1 and already is the
+module's product identity, so the shell renders it instead of the module id. `suggestedGroup` was
+deferred rather than shipped — it would force a hard manifest-version cutover for a hint, and its
+only correct semantics needs initialization logic that risks a suggestion overwriting an
+administrator's decision.
+
+Core owns the persistence: two `ekklesia_core_dashboard_*` tables (migration `0003`) holding groups
+and placements, platform-global because no organization model exists yet. `group_id` is
+`on delete set null`, so deleting a group ungroups its modules and a dangling reference is
+impossible; `module_id` carries no foreign key, because modules are packages rather than rows, so a
+placement for an uninstalled module is retained and restores its position on reinstall.
+`resolveDashboardNavigation` is a pure function of configuration plus the mountable set: an unplaced
+module is ungrouped and visible with no initialization write, an absent module renders nothing,
+empty groups are kept, and ordering is total with the identifier as final tie-break.
+
+`GET /api/v1/dashboard/navigation` returns the resolved view, layered **on top of** the host-neutral
+module UI inventory rather than merged into it — it embeds each generic descriptor untouched, so a
+standalone host consuming the inventory never inherits Dashboard semantics. Reading requires the same
+permission the inventory does; organizing requires the new platform permission
+`core.dashboard.navigation.manage` through a narrow, structured, idempotent mutation contract. The
+shell renders that arrangement and computes none of it.
+
+**Still not the finished Dashboard.** No editor or drag and drop, no nested folders, no icons, no
+Dashboard Home or widgets, no design system, and no client routing. A production CSP and a deployment
+for the built shell, sign-in UI, general asset publication, and the standalone host remain future
+work.
 Restart-based discovery, explicit operator-invoked migrations, and the trusted compiled-module model
 are all unchanged.