waitfor: block until a shell condition holds

--cmd exits 0 (+ optional --matches regex) or --timeout; exit 0/3/1,
last output always printed, --then hook composes with notifyr.
Injectable runner for tests + real-shell integration test.
Spec: doc/tool-parity.md 3.2.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011KikHkfCiC3yELbsMN8fT9

waitfor/README.md

@@ -0,0 +1,44 @@
+# waitfor — block until a condition holds
+
+Replaces the hand-rolled `while ! curl …; do sleep 5; done` loops that
+each need a fresh approval in an agent session with **one stable
+command prefix**. The agent makes one blocking call instead of burning
+turns polling. Closes the `Monitor` gap from
+[`doc/tool-parity.md`](../doc/tool-parity.md) §3.2.
+
+## Usage
+
+```
+waitfor --cmd "shell command" [--matches regex] [--interval 30s]
+        [--timeout 20m] [--then "shell command"] [--verbose]
+```
+
+The condition holds when `--cmd` exits 0 **and**, if `--matches` is
+given, its combined output matches the regex. The first attempt runs
+immediately; then every `--interval` until `--timeout`.
+
+| Exit | Meaning |
+|------|---------|
+| 0 | condition met (`--then` runs afterwards, if given) |
+| 3 | timeout — last output still printed so the caller sees the state |
+| 1 | usage/config error (empty `--cmd`, bad regex) |
+
+Examples:
+
+```bash
+# wait until Gitea answers again
+waitfor --cmd "curl -sf https://gitea.brasse-pc.eu/api/healthz" --interval 30s --timeout 20m
+
+# wait until a container is listed (read-only Pi5 wrapper)
+waitfor --cmd "ssh pi5-claude sudo claude-docker ps" --matches gitea --timeout 10m
+
+# wait for a file, then notify the phone (composes with notifyr)
+waitfor --cmd "test -f /tmp/report.html" --then 'notifyr send --msg "report is ready"'
+```
+
+## Build & test
+
+```bash
+go test ./...
+go build -o build/waitfor .
+```