feat: initial Lam Agent extension for Vicinae

Agentic AI chat inside the Vicinae launcher, powered by Ollama.

- chat: the search bar is the composer (Return sends), cmd+return opens a
  multi-line composer, answers stream into a markdown detail panel, the
  newest turn renders first, and Tab reaches a conversation switcher in
  the search bar accessory
- sessions: browse, reopen, copy, and delete past conversations
- setup: verifies the Ollama connection and lists the models the key can
  actually reach, rather than trusting a hand-typed model name
- tools: get_datetime, get_location, web_search, web_fetch. All read-only,
  and the tool-calling loop is capped at 5 rounds

Notes on two constraints that shaped the design:

The search bar is single-line and there is no API to change it, so
"Return sends" and "cmd+return inserts a newline" cannot both live in one
field. They are split across the search bar and a pushed Form instead.

An extension can read preferences but cannot write them, so setup hands
over the exact model name to paste rather than saving it.

The logic layer (ollama, agent, tools, location, history, markdown) holds
no Vicinae imports and is unit tested without a runtime; a test enforces
that boundary. 77 tests cover NDJSON chunk-boundary parsing, the tool
loop, session caps, and timezone handling.

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Adrian Bonpin
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.