feat: add context meter and file-based system prompts

Two additions to the chat window.

A context meter in the top bar shows how much of the active model's window
the next request will occupy: system prompt, prior turns, attachments and
the current draft. The router does not report a usable context size in
router mode (/props returns n_ctx 0), so the limit comes from ctx-size in
presets.ini. Streaming requests now ask for usage statistics, which makes
the figure exact after each reply at no extra round trip; before that it is
an estimate marked with a leading ~.

The estimate reads low on models with a reasoning budget, since thinking
tokens cannot be known before the reply arrives. The tooltip says so.

System prompts are markdown files in the prompts/ directory beside the
config, one per file, so they can be edited in an editor and kept in
version control. default.md is global, any other file is a named preset
that replaces it rather than adding to it, and a conversation may instead
carry one-off text or opt out entirely. The choice is stored per session so
reopening a chat restores the prompt it was built with.

Prompt names are reduced to safe filenames, so a name like ../../etc/passwd
cannot write outside the prompts directory, and a name that reduces to
nothing is rejected rather than creating a dotfile.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a7435e3..1b71e76 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,28 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Context meter in the top bar showing how much of the active model's
+  context window the next request will use. It estimates while typing and
+  switches to the server's exact token counts after each reply, turning
+  amber at 75% and red at 90%. The limit comes from `ctx-size` in
+  `presets.ini`, since the router does not report it.
+- System prompts stored as markdown files in `~/.config/llamachat/prompts/`.
+  A global `default.md` applies to new conversations, named presets replace
+  it, and any conversation can take a one-off custom prompt or none at all.
+  A dialog behind the picker adds, edits and deletes them; the files stay
+  editable outside the app.
+- `default_prompt` in `config.toml` chooses what new conversations start
+  with.
+- Streaming requests now ask for usage statistics, which is what makes the
+  meter exact without an extra round trip.
+
+### Changed
+
+- Sessions record the system prompt they were built with, so reopening a
+  conversation restores it rather than applying whatever is selected now.
+
 ## [0.1.0] - 2026-07-31
 
 First working version.