fix(addons): one page title, one primary action and clearer empty states (#12850)

A visual pass over the add-on pages found the same few problems on
several of them. Fix them with one rule per problem instead of page by
page.

Titles: every add-on page takes the host page-title size. Talk and Tables
no longer shrink it, Studio draws one "Studio" title above its tabs (the
card of a generator is a section), and Voice keeps one title on all its
tabs. The Text to speech tab gets a styled form. The "not available"
page shows the add-on name, not the lowercase id, and sits at the same
inset as an add-on page.

One primary action: the empty state of a list carries the add button, so
the header button waits until there is something in the list (Voice
library, enrolling a speaker or a person, Add rows). The Add-ons page
shows one way into Browse. A table with no columns says so once.

Tables: Share is hidden when there are no named accounts. The active
table tab is highlighted and an empty tab list leaves no gap before
"New table".

Studio: the tab strip stays on one row at 1280 wide, /studio/3d opens
the 3D tab, and an input chip has a divider between its label and its
placeholder.

Fine-tune and Quantize: the Experimental badge sits beside the lede, not
inside the h1; an open step shows its number instead of an empty circle;
the sticky action bar keeps a gap above it.

The footer shows nothing for the empty version of a source build, and
the Voice Text to speech tab says where to get a model when none is
installed.

Assisted-by: Claude:claude-sonnet-5-5 [Claude Code]

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>

scripts/addons/suites.json

@@ -2995,6 +2995,9 @@
       "unit: batch: every cell error is named by row and column and nothing is sent",
       "unit: batch: steps stay inside the add-on bounds",
       "unit: batch: the selection toggles by row identifier and survives paging",
+      "unit: layout: Share is offered only where the installation has named accounts",
+      "unit: layout: a table with no rows offers Add rows once, in its empty state",
+      "unit: layout: a reader, or a table with no columns, is offered no Add rows",
       "unit: errors: each answer of the host gets its own words and recovery",
       "unit: codecs: text keeps what was typed, bounds it, and null is explicit",
       "unit: codecs: integers are exact up to 64 bits and never silently rounded",