docs(changelog): record the 2026-07-29 composer and system-prompt batch (#123)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

changelog/unreleased/README.md

@@ -8,6 +8,12 @@ Changes since v0.1.4. The version number is assigned at release, when this folde
 
 - [2026-07-29] Core and tooling: `PORT` / `HOST` and the internal CLI plumbing no longer reach commands the Agent runs, so a dev server started by `exec_command` picks its own port instead of binding the harness's; and the development backend moves to 7368, so `pnpm dev` no longer collides with an installed `penguin web` — or, quieter and worse, proxies to it. ([details](2026-07-29-harness-env-and-dev-ports.md))
 
+- [2026-07-29] Web App: the composer can attach files of any type — written to the Session scratchpad and handed to the model as `[attached file: <path>]` lines, keeping non-ASCII names — and the `@` mention becomes an `/agent` command; both switch commands are session-only and stage their pick as a chip, cached with the text, until Enter sends. ([details](2026-07-29-composer-attachments-and-switch-commands.md))
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+- [2026-07-29] Core: the default system prompt is about a tenth shorter (1087 → 969 words), with the trim concentrated in the sections re-read every turn. It now pins replies to the user's language, states the API-key stop rule once, points at parallel subagents for large tasks, and has tooling installed once into a shared per-Agent `shared_env/` directory while project dependencies stay in the project. The App Data Dir rule also stops forbidding deliverables in a tree that a temporary Workspace lives inside. Existing Agents keep their own prompt. ([details](2026-07-29-default-system-prompt.md))
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+- [2026-07-29] Web App: the chat header's elapsed chip no longer restarts from zero when a running Session is reloaded and now counts an event still in flight, and a round interrupted before its first Request settles to the same figure whether it was watched live or replayed — the running Task is anchored to the server's own clock instead of the browser's. ([details](2026-07-29-session-elapsed.md))
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 - [2026-07-28] Web App: model configuration stops inviting the browser's saved login — every form control opts out of autofill unless it declares a real credential role, and a secret field says `new-password`, the only value Chrome and Safari honor on a password box; a closed docked side panel no longer paints its 1px divider next to the open one, which read as a second, empty panel beside the Workspace files; a provider-signature message carrying no text stops drawing an empty reply bubble after a thinking segment; Benchmark costs now follow the display currency selected in settings; the tool card states a call's outcome once instead of twice; and no page can grow the document into a second scrollbar that drags the whole shell. ([details](2026-07-28-web-app.md))
 
 - [2026-07-28] Web App and CLI: duration and byte abbreviations now carry into the next unit instead of printing `1m60s` or `1024KB` — both helpers rounded the value they displayed but chose the unit (or the minute/second split) from the raw input. ([details](2026-07-28-duration-and-byte-formatting.md))