AIFS Single virtual quickstart: require dynamical-catalog 1.0.0 and tighten the intro

[mrshll]

Updates the AIFS Single virtual quickstart for the v0.2.0 store, whose virtual chunk references point into ECMWF's Google Cloud mirror (gs://ecmwf-open-data/), with s3://ecmwf-forecasts/ as a second container for the init times the mirror lacks.

Changes

• Install line (cell 1): 'dynamical-catalog>=1.0.0'. 1.0.0 is the first release that reads a non-S3 virtual chunk container. Without a floor, uv pip install leaves an already-installed 0.8 in place.
• Introduction (cell 0): the version note now says >=1.0.0, matching the collection description, and the introduction states the coverage (April 2024 to present), which AGENTS.md asks for.
• Structure note (cell 3): removed the chunking bullet and the latitude/longitude sentence, because AGENTS.md says to leave out storage internals and what the repr already shows. The note that pressure-level variables live in the pressure_level group stays, since ds does not show it.

No other cell and no stored output changed in this pull request. It merged at 16:04Z on 2026-09-17, before the gap fill in dynamical-org/reformatters#1070 published, so its stored outputs are still the ones rendered against v0.1.0.

Follow-ups

• Regenerate the AIFS Single virtual quickstart outputs against v0.2.0 #77 regenerates the outputs against the filled v0.2.0 store.
• AIFS Single virtual quickstart: read the production catalog #76 removes the staging catalog URL from cell 2, to merge once Promote ecmwf-aifs-single-forecast-virtual (v0.2.0) to production dynamical-stac#108 has published the dataset to production.

Checks

check_install_lines.py and the unit tests passed, and the notebook validated with 21 cells, unchanged in order.