feat: add weather skill (wttr.in + Open-Meteo fallback)

No API key required. Two services:
- wttr.in: human-readable, emoji, ASCII art, PNG
- Open-Meteo: JSON API fallback for programmatic use

🌤️🦞

skills/weather/SKILL.md

@@ -0,0 +1,49 @@
+---
+name: weather
+description: Get current weather and forecasts (no API key required).
+homepage: https://wttr.in/:help
+metadata: {"clawdis":{"emoji":"🌤️","requires":{"bins":["curl"]}}}
+---
+
+# Weather
+
+Two free services, no API keys needed.
+
+## wttr.in (primary)
+
+Quick one-liner:
+```bash
+curl -s "wttr.in/London?format=3"
+# Output: London: ⛅️ +8°C
+```
+
+Compact format:
+```bash
+curl -s "wttr.in/London?format=%l:+%c+%t+%h+%w"
+# Output: London: ⛅️ +8°C 71% ↙5km/h
+```
+
+Full forecast:
+```bash
+curl -s "wttr.in/London?T"
+```
+
+Format codes: `%c` condition · `%t` temp · `%h` humidity · `%w` wind · `%l` location · `%m` moon
+
+Tips:
+- URL-encode spaces: `wttr.in/New+York`
+- Airport codes: `wttr.in/JFK`
+- Units: `?m` (metric) `?u` (USCS)
+- Today only: `?1` · Current only: `?0`
+- PNG: `curl -s "wttr.in/Berlin.png" -o /tmp/weather.png`
+
+## Open-Meteo (fallback, JSON)
+
+Free, no key, good for programmatic use:
+```bash
+curl -s "https://api.open-meteo.com/v1/forecast?latitude=51.5&longitude=-0.12&current_weather=true"
+```
+
+Find coordinates for a city, then query. Returns JSON with temp, windspeed, weathercode.
+
+Docs: https://open-meteo.com/en/docs