A SimpleX Chat bot that answers arithmetic (closes #1)

Remove the template's HTTP service, database and fx wiring. Add exact
arithmetic on go/parser and go/constant, a client that runs simplex-chat
as a child process and drives its WebSocket API, and the bot, which keeps
an auto-accepting address and replies to each message. The image adds the
checksum-pinned simplex-chat v7.0.2 on Ubuntu 22.04.

Model: opus-5-5

AGENTS.md

@@ -1,6 +1,6 @@
 ---
 title: Agent Guidance
-last_modified: 2026-08-22
+last_modified: 2026-09-26
 ---
 
 This file is the single source of guidance for any automated agent
@@ -15,18 +15,20 @@ configuration, instructions or notes addressed to one particular tool.
 Guidance goes here instead, written so that any agent can follow it.
 
 Nothing in this repository names an assistant, model or vendor in its
-prose. That rule propagates: every project seeded from this template
-inherits it.
+prose.
 
 Read `docs/REPO_POLICIES.md` as well. Where this file and that one
 overlap, they agree; where this file is silent, that one governs.
 
 ## What this repository is
 
-A template. It is a working HTTP service — it builds, tests, lints and
-runs — whose purpose is to be copied. Nothing in it is precious. The
-`widgets` table, the index page and the debug panic route are there to
-prove the machinery works end to end, and are meant to be deleted.
+A SimpleX Chat bot that answers arithmetic. The Go program starts the
+SimpleX Chat command-line client (`simplex-chat`) as a child process,
+drives it over its local WebSocket API, gives the bot a long-term
+contact address that accepts every contact request, and replies to each
+text message with the value of the arithmetic in it. Both ship in one
+container image; the SimpleX database lives on a volume. It was seeded
+from `go-template-repo` and keeps that template's gates and conventions.
 
 ## Iron rules
 
@@ -56,17 +58,15 @@ regardless of what else it achieves.
 
 5. **Never use scripted search-and-replace to edit files** — no
    `sed -i`, `perl -pi`, `awk` rewrites, or scripted heredocs. Read the
-   file and edit it, even when there are many similar edits. The single
-   exception is `script/rename`, which is a tool an operator runs once,
-   against a known-shaped tree, at seed time — and which deletes itself
-   afterwards.
+   file and edit it, even when there are many similar edits.
 
 6. **Formatting only via `make fmt`.** Never hand-roll a reformat.
    `make fmt-check` is the read-only form and must stay non-mutating.
 
 7. **Pin every external reference by hash.** Docker base images by
-   `@sha256:`, Actions by commit SHA, Go modules by `go.sum`. A version
-   tag is server-mutable and therefore remote code execution.
+   `@sha256:`, Actions by commit SHA, Go modules by `go.sum`, the
+   `simplex-chat` download by the checksum on its `ADD`. A version tag
+   is server-mutable and therefore remote code execution.
 
 8. **Clean up every container and image you create. Never run
    `docker builder prune`, `docker image prune`, or any other prune.**
@@ -104,9 +104,11 @@ Do not weaken them.
 ## Branching model
 
 - `main` is the default branch and is kept green.
-- Work happens on a branch off `main`.
-- Merge to `main` directly when the branch is not protected; otherwise
-  open a PR.
+- `next` integrates work toward the next release: branch from `next`,
+  merge back to `next`. Before 1.0.0, green work may also land directly
+  on `main`.
+- Merge directly when the target branch is not protected; otherwise open
+  a PR.
 - `docs/TODO.md` changes go in the same commit as the work they
   describe.
 - Push finished work to the remote. Work that exists only locally is
@@ -116,63 +118,35 @@ Do not weaken them.
 ## Layout
 
 ```
-cmd/simplexcalc/       cobra command tree; main() and serve
-internal/app/         the fx object graph — the only place that knows
-                      which concrete type satisfies what
-internal/config/      viper-backed configuration; the abort-on-garbage rule
-internal/database/    sqlite handle, embedded schema, migration runner
-internal/globals/     build-time metadata (ldflags)
-internal/handlers/    HTTP handlers, one struct, fx-injected dependencies
-internal/logger/      log/slog, JSON always
-internal/middleware/  request id, logging, metrics, recovery, timeout,
-                      body cap, security headers, CSRF
-internal/render/      template compilation and execution
-internal/server/      lifecycle, route table, static file serving
-internal/telemetry/   Sentry and Prometheus
-templates/            go:embed HTML: base document, pages, partials
-static/               go:embed CSS and JS
-script/               the entrypoints
+cmd/simplexcalc/    cobra command tree; main(), run and version
+internal/bot/       startup, address setup, and the reply to a message
+internal/calc/      the arithmetic: go/parser and go/constant
+internal/config/    viper-backed configuration; the abort-on-garbage rule
+internal/logger/    log/slog, JSON always
+internal/simplex/   the simplex-chat child process and its WebSocket API
+script/             the entrypoints
 ```
 
 ## Conventions
 
-- **Dependency injection through `fx`.** A constructor takes an
-  `fx.Lifecycle` and a `Params` struct; it never reaches for a
-  package-level singleton. Returning an error from a constructor aborts
-  startup, which is how configuration failures become refusals to start.
 - **Logging is `log/slog` only.** Never `zerolog`, never `logrus`. JSON
-  output in every environment. `net/http`'s own error output is routed
-  through the same handler so that one process emits one format.
+  output in every environment. The chat client's own output is logged
+  line by line through the same handler, so that one process emits one
+  format.
 - **Errors wrap with `%w`** and are compared with `errors.Is`. Sentinel
-  errors are package-level `var`s named `errThing`.
-- **A handler never shows an error's text to a client.** The client gets
-  a chosen message; the error goes to the log and to Sentry, joined by
-  the request id that is also in the response header.
-- **Route labels in metrics are chi route PATTERNS, never paths.**
-  Labelling by path makes every distinct URL a new time series, and a
-  crawler then owns the process's memory.
-- **Tests exercise behaviour, not implementation.** The server tests
-  start a real listener against a real database and speak HTTP to it.
-  Prefer that over asserting on internals.
+  errors are package-level `var`s.
+- **A reply never shows an error's text to a contact.** The contact gets
+  a chosen sentence; anything unexpected goes to the log.
+- **Unknown chat client records are ignored, never fatal.** The SimpleX
+  API adds fields and record types between releases, and its
+  documentation requires clients to skip what they do not know. Decode
+  only the fields that are read.
+- **A failure of the chat client or the connection to it ends the
+  process with an error**, so the container's restart policy restarts
+  both together. There is no reconnect loop.
+- **Tests exercise behaviour, not implementation.** The client tests
+  speak the real WebSocket protocol to a stand-in chat client. Prefer
+  that over asserting on internals.
 - **Comments explain why, and traps.** Delete the history, the
   reasoning-out-loud and the self-justification; keep what a reader
   needs in order not to fall in.
-
-## What to change when seeding a new project
-
-1. Clone, then run `script/rename <newname> [module-path]` on a clean
-   tree. It rewrites the placeholder name and module path everywhere,
-   renames `cmd/simplexcalc`, and deletes itself. Review the diff.
-2. Delete the example domain:
-   `internal/database/schema/001_widgets.sql`,
-   `internal/database/model_widget.go`, the widget parts of
-   `internal/handlers/index.go` and `templates/index.html`, and their
-   tests. Start your own schema at `001`.
-3. Rewrite `README.md` for the new project. It currently describes the
-   template, which the new project is not.
-4. Rewrite this file's "What this repository is" section, and delete
-   this list. Keep the iron rules, the entrypoints, the branching model
-   and the conventions — they are why the template exists.
-5. Reset `docs/TODO.md`: keep the Workflow section, replace the rest.
-6. Decide on `CSRF_KEY` and the metrics credentials before the first
-   deployment. See `README.md` for what each one does when unset.