Knowledge bases, and a file input that lines up

**Bases.** Documents now live in named collections rather than one flat pile,
and a chat can be pointed at particular ones — "answer from the contracts
folder" is a different question from "answer from everything I have ever
uploaded". A chat with none attached still searches everything its owner can
see, because empty means unscoped, not empty.

The harness names the attached bases. Without that the model cannot tell "there
is nothing about this" from "I am only allowed to see one folder", and it
phrases a miss as the former.

**Sharing moves to the base.** A document is visible to whoever can see the base
it lives in, so `Document` is gone from the shareable types and
`documents.visible()` filters through `base_id`. "This folder is the team's" is
the granularity people think in; per-document grants meant answering "who can
see this?" by checking every file. Moving a document between bases changes who
can see it, so the destination has to be one you own.

`Document.base_id` is nullable only because the column had to be added to a
table that already had rows. `sweep_unfiled()` runs at startup beside the
orphaned-upload sweep and files anything predating bases into its owner's
default, which is what makes "always set" true everywhere else.

**The file input.** `.input` gave it a fixed height and horizontal padding, so
the browser's own button sat hard against the left edge while the filename
floated off the centre line. A file input is two controls in one box and
neither inherits anything useful, so it gets its own rule: no horizontal
padding, the button sized to `--control-h` with the divider that separates it,
and the text centred with line-height rather than flexbox, which file inputs do
not lay out reliably.

437 tests, ruff clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

PLAN.md

@@ -6,7 +6,7 @@ that would be expensive to revisit. Kept current as work lands; the detail of
 
 **Status:** usable daily. Streaming chat, attachments, reasoning, tool calling
 with web search, a knowledge library, notes, memory and skills, speech in and
-out, users and groups, model administration, installable as an app. 428 tests,
+out, users and groups, model administration, installable as an app. 437 tests,
 `ruff` clean.
 
 ---
@@ -59,8 +59,11 @@ be a different project, not a refactor.
       the next turn, for the same reasons reasoning is not
 
 ### The library
-- [x] **Knowledge** — documents, images and saved web pages, ingested through
-      the same pipeline as chat attachments, searched with SQLite FTS5
+- [x] **Knowledge bases** — documents, images and saved web pages, grouped into
+      named collections and ingested through the same pipeline as chat
+      attachments, searched with SQLite FTS5
+- [x] A chat can be pointed at particular bases, so "answer from the contracts
+      folder" is a different question from "answer from everything I have"
 - [x] **Notes** — longer things the model writes down and searches later;
       editable by hand, because they are yours
 - [x] **Memory** — short facts, injected on every turn to a budget rather than
@@ -70,8 +73,9 @@ be a different project, not a refactor.
 - [x] A model may write and revise its own notes, memories and skills. Every
       skill revision is kept, attributed and revertible — the safety story is a
       record and a way back, not a gate
-- [x] **Sharing** — any of the three can be shared with a group or with named
-      people, read-only. One visibility rule, and administrators do not bypass it
+- [x] **Sharing** — a knowledge base, a note or a skill can be shared with a
+      group or with named people, read-only. One visibility rule, and
+      administrators do not bypass it. Documents are shared through their base
 - [x] **The harness** — an operational prompt assembled from what a model
       actually has, so the tools get used rather than ignored
 - [x] Attach menu: file, image, a web page fetched on the spot, or a document