docs(fallback): use fallback_providers list shape throughout

[Aman113114-IITD]

The user-guide fallback-providers page primarily showed the legacy 'fallback_model:' singular key in every example, with only a small note pointing at the canonical top-level 'fallback_providers:' list. The code path (and 'hermes fallback' CLI) writes the list shape, and environment-variables.md was already cleaned up to reflect this.

Rewrite the page so every example uses 'fallback_providers' as a top- level list, invert the comparison note to describe 'fallback_providers' as canonical and 'fallback_model' as legacy back-compat, add a multi-entry example to show chaining, and fix the summary table row.

Refs #19691

What does this PR do?

Related Issue

Fixes #

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

How to Test

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform:

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — or N/A
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

For New Skills

• This skill is broadly useful to most users (if bundled) — see Contributing Guide
• SKILL.md follows the standard format (frontmatter, trigger conditions, steps, pitfalls)
• No external dependencies that aren't already available (prefer stdlib, curl, existing Hermes tools)
• I've tested the skill end-to-end: hermes --toolsets skills -q "Use the X skill to do Y"

Screenshots / Logs

[alt-glitch]

Duplicate of #26017 / #23163 — both address the same fallback_providers docs alignment for #19691. Same file (fallback-providers.md), same change.

[teknium1]

This looks implemented on current main by the earlier fallback-docs alignment work. Automated hermes-sweeper review.

Evidence:

• website/docs/user-guide/features/fallback-providers.md:32 now tells users to configure a top-level fallback_providers list and shows the list-shaped YAML.
• website/docs/user-guide/features/fallback-providers.md:42 documents fallback_providers as the current multi-fallback shape and fallback_model as legacy back-compat.
• website/docs/user-guide/features/fallback-providers.md:413 updates the summary table to fallback_providers: as the top-level list config location.
• Commit 175885218e82f99fb3cb58335640b7d4f4b7c2f8 made this docs alignment and closes the underlying docs mismatch issue Fallback provider docs show stale/incorrect config paths for fallback_providers #19691.
• A maintainer comment on this PR already noted it duplicates fix(docs): align fallback provider config examples #26017 / docs(fallback): align feature guide with fallback_providers #23163 for the same file and same fallback-provider docs alignment.