types: clear remaining tsc errors across 41 files (76→14, behavior-preserving)

Per-file type-only fixes surfaced after the Supabase client was correctly
typed. All fixes preserve runtime behavior; no any/ts-ignore/ts-expect-error.

- lib/supabase/client.ts: annotate the browser client as SupabaseClient<Database>
  (same ssr/js drift as server.ts; fixes it centrally for all callers).
- Supabase embedded-select joins whose FK metadata is missing from the
  generated types are bridged with `as unknown as <target>` + a TODO to remove
  after regenerating types/database.ts.
- setState optimistic-update variance and raw <select> enum values cast to the
  precise element/union type; .insert payload fields (Json, enums) given the
  precise column type via satisfies/field casts.
- Added narrowing guards where a value was legitimately nullable (comms channel,
  public form page) without changing the intended path.

The 14 remaining errors are confined to the four files fixed in Phase B (real
bugs + the tautological actions.test rewrite). 639 tests still green.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

app/(app)/comms/comms-client.tsx

@@ -85,11 +85,11 @@ export default function CommsClient({ member, space, channels }: Props) {
                 m.id.startsWith('temp-') &&
                 m.user_id === payload.new.user_id &&
                 m.content === payload.new.content
-                  ? payload.new
+                  ? (payload.new as Message)
                   : m,
               )
             }
-            return [...prev, payload.new]
+            return [...prev, payload.new as Message]
           })
         },
       )
@@ -105,6 +105,7 @@ export default function CommsClient({ member, space, channels }: Props) {
   }, [messages])
 
   async function loadMessages() {
+    if (!selectedChannel) return
     const supabase = createClient()
     const { data } = await supabase
       .from('comms_messages')
@@ -119,6 +120,7 @@ export default function CommsClient({ member, space, channels }: Props) {
     e.preventDefault()
     const content = newMessage.trim()
     if (!content || sending) return
+    if (!selectedChannel) return
     setSending(true)
 
     // Optimistic insert — message appears immediately for the sender
@@ -133,7 +135,7 @@ export default function CommsClient({ member, space, channels }: Props) {
       content,
       created_at: new Date().toISOString(),
     }
-    setMessages(prev => [...prev, optimisticMsg])
+    setMessages(prev => [...prev, optimisticMsg as Message])
     setNewMessage('')
 
     const supabase = createClient()
@@ -142,7 +144,7 @@ export default function CommsClient({ member, space, channels }: Props) {
       .insert({
         channel_id: selectedChannel.id,
         space_id: space?.id ?? member.space_id,
-        user_id: member.user_id,
+        user_id: member.user_id as string,
         display_name: member.display_name,
         handle: member.handle,
         content,

app/(app)/comms/page.tsx

@@ -1,4 +1,5 @@
 import { createClient } from '@/lib/supabase/server'
+import type { Tables } from '@/types/database'
 import CommsClient from './comms-client'
 
 export default async function CommsPage() {
@@ -17,5 +18,5 @@ export default async function CommsPage() {
     .order('channel_type')
     .order('name')
 
-  return <CommsClient member={member} space={member?.spaces} channels={channels ?? []} />
+  return <CommsClient member={member} space={member?.spaces as Tables<'spaces'>} channels={channels ?? []} />
 }