Add root README.md (project overview + local Docker quickstart for ychat)

The repo holds three legacy C++ subprojects (ychat, yhttpd, ycurses). Add a
root README that explains them, points at ./ychat (the revived/deployed
chat) and its DOCKER.md, and gives a detailed local Docker build/run/access
quickstart plus f3s deploy pointer.

Also fix the now-stale 'HTTP/0.9 responses' note in ychat/DOCKER.md: ychat
emits proper HTTP/1.1 responses since the reqp.cpp header fix.

1 files changed, 126 insertions, 0 deletions

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+# ychat / yhttpd / ycurses
+
+This repository collects three small, legacy C++ projects by Paul C. Buetow
+(originally ~2003–2007). They share a common socket/event/template engine and
+are kept here as historical/revival code.
+
+| Subproject | What it is | Status |
+|------------|------------|--------|
+| [`./ychat`](ychat/)   | An HTTP-based web chat server (browsers are the clients; CSS/HTML/JS only). | **Revived & deployed** — builds in Docker, runs on the f3s k3s cluster. |
+| [`./yhttpd`](yhttpd/) | A tiny standalone http server derived from ychat's socket/threading engine. | Unrevived (see its own tree). |
+| [`./ycurses`](ycurses/) | A curses front-end experiment. | Unrevived (see its own tree). |
+
+The detailed, up-to-date build/deploy notes for the chat live in
+[`./ychat/DOCKER.md`](ychat/DOCKER.md). The rest of this file is a quickstart
+for running **ychat** locally in Docker and accessing it.
+
+> The ychat tree has been substantially fixed during this revival (legacy-C++
+> build fixes, a from-scratch streaming-chat layer, and a security/bug sweep).
+> See `git log` under `./ychat` and `./ychat/DOCKER.md` for the full list.
+
+---
+
+## Quickstart: run ychat locally in Docker
+
+You need a container runtime (`podman` or `docker`). The build is a
+multi-stage `Dockerfile` (Rocky Linux 9 builder + slim Rocky 9 runtime) that
+compiles ychat **entirely inside the container** — no host toolchain required.
+
+### 1. Build the image
+
+From the **repository root**:
+
+```sh
+cd ychat
+podman build -t ychat:dev .
+# or:  docker build -t ychat:dev .
+```
+
+The build configures ychat with all optional features off (no SSL, no MySQL,
+no readline) — this is "Mode A": an **in-memory guest chat with no account
+database**. The default chat port is **2000**.
+
+### 2. Run it
+
+```sh
+podman run --rm -p 2000:2000 --name ychat ychat:dev
+# or:  docker run --rm -p 2000:2000 --name ychat ychat:dev
+```
+
+The server logs to stdout. You should see something like:
+
+```
+yChat 0.9.0-CURRENT Build ...
+Sock: Created socket on localhost:2000
+Sock: Server socket is ready
+Initializing sock events (1)
+```
+
+### 3. Access it
+
+Open http://localhost:2000/ in a browser.
+
+- You'll get the **guest login page** (no password field, no "Register" link —
+  there is no account database in this build).
+- Enter any alphanumeric nick (e.g. `alice`), leave the room as `Lounge`, and
+  click **login**.
+- The chat frameset loads: a streaming message view, the online-user list, and
+  an input box. Type a message and hit **Send** — it appears in the stream.
+- Open a second browser/window with a different nick in the same room to see
+  messages delivered to both clients in real time.
+
+Quick CLI checks:
+
+```sh
+# the login page (HTTP/1.1, 200):
+curl -sS http://localhost:2000/ -o /dev/null -w '%{http_code}\n'
+
+# log in and grab a session tmpid:
+curl -sS -X POST -d 'event=login&nick=alice&room=Lounge&end=end' \
+     http://localhost:2000/frameset.html
+```
+
+### 4. Stop it
+
+```sh
+podman rm -f ychat
+# (Ctrl-C also stops the foreground `run` above)
+```
+
+---
+
+## Notes on the local run
+
+- **State is in-memory only.** With no database, all users/sessions/rooms live
+  in RAM and are wiped on container restart. That's intentional for the
+  revival; `chat.enableguest=true` lets anyone log in with just a nick.
+- **Logs** go to `/app/log/` inside the container (`access_log`, `system_log`,
+  `rooms/<room>`). They're an `emptyDir` in k8s and a container-local dir
+  locally, so they don't persist after `rm`.
+- **Configuration** is `ychat/etc/ychat.conf`, baked into the image at
+  `/app/etc/ychat.conf`. You can override any config key at runtime with
+  `-o <key> <value>` (the image already does this for
+  `chat.session.md5hash=false` and `httpd.startsite=index_guest.html`).
+  Example: `podman run --rm -p 2000:2000 ychat:dev /app/bin/ychat -o chat.idle.timeout 300`.
+- **No operator commands for guests.** The default-operator escalation
+  (`/exec` shell RCE) was removed for security; in this no-DB build there is no
+  authenticated operator, so privileged commands (`/ko`, `/ban`, `/exec`, …)
+  are unavailable by design.
+
+---
+
+## Deploying to the f3s k3s cluster
+
+This is covered in detail in [`./ychat/DOCKER.md`](ychat/DOCKER.md). In short:
+the image is pushed to the f3s private registry
+(`r0.lan.buetow.org:30001/ychat:<tag>`), and a Helm chart + ArgoCD Application
+in the [`conf` repo](https://codeberg.org/snonux/conf) (path
+`f3s/ychat/helm-chart`) deploy it. The LAN URL is
+**https://ychat.f3s.lan.buetow.org/**.
+
+---
+
+## License
+
+GPL-2.0 (see [`./ychat/COPYING`](ychat/COPYING)). Source:
+https://codeberg.org/snonux/ychat
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