[Feature] Add IEM-backed national NWS text products

[Orinks]

Summary

Add support for retrieving accessible national NWS text products through Iowa Environmental Mesonet (IEM) APIs, with an initial focus on SPC and related national products.

Motivation

A prospective AccessiWeather user asked about IEMBot/IEM as a way to retrieve SPC and other national weather products without scraping web pages. This would be useful for weather enthusiasts who want accessible, screen-reader-friendly access to products such as SPC outlooks, mesoscale discussions, watches, WPC discussions/outlooks, and other national text products.

Proposed Solution

Create an IEM-backed provider for national NWS text products and structured SPC/WPC data.

Potential initial paths:

• Raw NWS text products via IEM AFOS retrieve service:
  • https://mesonet.agron.iastate.edu/cgi-bin/afos/retrieve.py?pil=SWODY1&fmt=text&limit=1
  • Supports AWIPS/PIL lookups such as SWODY1, SWODY2, AFDxxx, and other 3-6 character product IDs.
  • Supports date ranges, ordering, text/html/zip output, and optional center/WMO disambiguation.
• Structured SPC outlooks:
  • https://mesonet.agron.iastate.edu/json/spcoutlook.py?lat=38.907&lon=-77.037&day=1&current=1
• Structured SPC mesoscale discussions:
  • https://mesonet.agron.iastate.edu/json/spcmcd.py?lat=42.0&lon=-95.0
• Other IEM services listed in their API index include SPC watches, SPC/WPC outlooks, WPC mesoscale precipitation discussions, local storm reports, SPS, and generic text product search/retrieval.

A good first UI could be a "National Products" or "NWS Text Products" view with curated entries for:

• SPC Day 1-8 convective outlooks
• SPC mesoscale discussions
• SPC watches
• WPC excessive rainfall / winter / precipitation discussions where available
• Raw AWIPS/PIL lookup for advanced users

Accessibility Considerations

These products are mostly text-first, which is a strong fit for AccessiWeather. The UI should preserve headings/sections, provide readable plain text, expose issue/valid times clearly, and avoid forcing users through maps or images to understand the hazard content.

For structured outlook responses, summarize the categorical risk and timing in accessible text while still allowing users to open the full official text product.

Additional Context

IEM API/docs references:

• IEM API index: https://mesonet.agron.iastate.edu/api/
• IEM AFOS retrieve API: https://mesonet.agron.iastate.edu/cgi-bin/afos/retrieve.py?help=
• IEM SPC outlook API: https://mesonet.agron.iastate.edu/json/spcoutlook.py?help=
• IEM SPC mesoscale discussion API: https://mesonet.agron.iastate.edu/json/spcmcd.py?help=

Caveat: IEM services are provided as-is and should be treated as a third-party data source. Prefer official NWS/API sources where they provide clean structured data, but IEM appears valuable for avoiding scraping and for archive/retrieval workflows.

[Orinks]

Follow-up direction from testing the Forecaster Notes/IEM work:

• Keep this issue open for the broader IEM-backed national text product work.
• Retire the existing Nationwide Discussions location/settings path rather than continuing to maintain it as a separate feature surface.
• Expose nationwide discussions from Forecaster Notes instead, alongside the local/current forecaster notes workflow.
• Use IEM AFOS plain text (mt=text) for national discussion products where possible instead of scraping HTML.
• Candidate PILs for the nationwide discussion set: PMDSPD, PMDEPD, QPFPFD, PMDMRD, SWODY1, SWODY2, SWODY3, TWOAT, and TWOEP.
• Advanced Lookup remains the place for arbitrary/historical products; the main Forecaster Notes dialog should focus on current relevant notes and discussions.

[Orinks]

Implemented in the current text products work, so closing this out.