feat(skills): add optional weather skill

Current conditions + multi-day forecasts via the keyless Open-Meteo
APIs (geocoding + forecast). Pure-stdlib script (urllib/json/argparse),
metric/imperial units, text or JSON output, WMO code mapping.
Inspired by the most-installed community weather skill; implemented
first-party from the Open-Meteo docs.

website/docs/user-guide/skills/optional/productivity/productivity-weather.md

@@ -0,0 +1,107 @@
+---
+title: "Weather — Current weather and forecasts via Open-Meteo, no API key"
+sidebar_label: "Weather"
+description: "Current weather and forecasts via Open-Meteo, no API key"
+---
+
+{/* This page is auto-generated from the skill's SKILL.md by website/scripts/generate-skill-docs.py. Edit the source SKILL.md, not this page. */}
+
+# Weather
+
+Current weather and forecasts via Open-Meteo, no API key.
+
+## Skill metadata
+
+| | |
+|---|---|
+| Source | Optional — install with `hermes skills install official/productivity/weather` |
+| Path | `optional-skills/productivity/weather` |
+| Version | `0.1.0` |
+| Author | Hermes Agent |
+| License | MIT |
+| Platforms | linux, macos, windows |
+| Tags | `Weather`, `Forecast`, `Utilities` |
+
+## Reference: full SKILL.md
+
+:::info
+The following is the complete skill definition that Hermes loads when this skill is triggered. This is what the agent sees as instructions when the skill is active.
+:::
+
+# Weather
+
+Look up current conditions and a multi-day forecast for any city using the
+free Open-Meteo APIs (geocoding + forecast), which require no API key. The
+script is pure Python standard library and prints a compact, chat-friendly
+text report.
+
+## When to Use
+
+- The user asks about current weather, temperature, wind, or precipitation
+  for a named place.
+- The user asks for a forecast ("what's the weather in Berlin this week?").
+- You need machine-readable weather data (`--format json`) for a follow-up
+  computation.
+
+## Prerequisites
+
+None beyond `python3` (3.8+). The script uses only the standard library
+(`urllib`, `json`, `argparse`) — no pip installs, no API key, no config.
+
+## How to Run
+
+Run through the `terminal` tool:
+
+```bash
+python3 ~/.hermes/skills/productivity/weather/scripts/weather.py "New York"
+```
+
+Common variants (same script path):
+
+```bash
+weather.py Berlin --days 7
+weather.py Tokyo --units imperial
+weather.py Paris --days 5 --format json
+```
+
+## Quick Reference
+
+| Flag | Values | Default | Meaning |
+| --- | --- | --- | --- |
+| `city` (positional) | one or more words | required | City name; multi-word names work quoted or unquoted |
+| `--days` | 1-16 | 3 | Number of forecast days |
+| `--units` | `metric`, `imperial` | `metric` | degC/km/h/mm vs degF/mph/inch |
+| `--format` | `text`, `json` | `text` | Compact text for chat, or raw JSON |
+
+## Procedure
+
+1. Run the script with the city name the user gave. Multi-word names are
+   joined automatically (`weather.py New York` works).
+2. If the user implies a unit preference (US locations often expect
+   Fahrenheit), pass `--units imperial`.
+3. Relay the output. The first line names the resolved location
+   (city, region, country) — mention it so the user can catch a wrong match.
+4. For programmatic needs, use `--format json` and parse the `location` and
+   `forecast` keys.
+
+## Pitfalls
+
+- **Geocoding ambiguity**: the script takes the top geocoding match
+  (e.g. "Springfield" resolves to Springfield, Missouri). Always echo the
+  resolved location line back to the user; add a state/country to the query
+  ("Springfield Illinois") to disambiguate.
+- **Rate limits**: Open-Meteo's free tier allows roughly 10,000 calls/day
+  for non-commercial use. Fine for chat usage; don't loop it in bulk jobs.
+- **WMO code coverage**: only the documented WMO weather codes are mapped;
+  an unexpected code prints as `Unknown (code N)` rather than failing.
+- **Failures**: city-not-found and network errors exit 1 with a message on
+  stderr — check the exit code, not just stdout.
+
+## Verification
+
+```bash
+python3 ~/.hermes/skills/productivity/weather/scripts/weather.py London --days 1
+```
+
+Expect a "Weather for London, England, United Kingdom" header, a "Now:"
+line, and one forecast line.