updated docs for showing runtime compatibility

[rafel-roboflow]

What does this PR do?

Adds documentation for the runtime compatibility mechanism that already lives in the workflow-block API (get_restrictions() / get_air_gapped_availability()), so block users can see — and block authors can understand — where each block degrades or fails outright.

Concretely, three things land together:

1. Hand-written prose section in docs/workflows/create_workflow_block.md (### Runtime restrictions) explaining Severity.SOFT / Severity.HARD, the three scoping axes (Runtime, StepExecutionMode, RuntimeInputMode), the shared presets (STATEFUL_VIDEO_HTTP_SOFT_RESTRICTION, COOLDOWN_HTTP_SOFT_RESTRICTION, STILL_IMAGE_INPUT_SOFT_RESTRICTION), and two concrete examples (preset reuse + a custom Severity.HARD restriction).
2. Auto-generated per-block "Runtime compatibility" section in the block gallery. The generator (development/docs/build_block_docs.py) now reads get_restrictions() and get_air_gapped_availability() off each manifest and renders them as a ### Runtime compatibility heading + ??? tip "Restrictions" admonition (matching the existing "Compatible Blocks" pattern), with a definition list inside that uses severity-colored Material icons (red shield for hard, amber alert-circle for soft, blue-grey cloud-off for requires_internet). Pages without caveats render no section at all, so existing blocks gain no boilerplate. Enabled the def_list markdown extension in mkdocs.yml to support the new layout.

And yet found another bug:
qwen3_5vl/v2.py was missing the get_restrictions() override that v1 already declared. v2's manifest extends WorkflowBlockManifest directly (not v1's BlockManifest), so nothing was inherited.

I also audited the rest of blocks trying to find other ones missing.

Related Issue(s): /resolve DG-521

Type of Change

• Documentation update
• Bug fix (non-breaking change that fixes an issue) — qwen3_5vl/v2.py missing get_restrictions() override

Testing

• I have tested this change locally
• I have added/updated tests for this change

Test details:
Tested and checked locally

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in hard-to-understand areas
• My changes generate no new warnings or errors
• I have updated the documentation accordingly (if applicable)

Additional Context

N/A

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Note

Low Risk
Mostly documentation and doc generation; the only runtime code change is declarative restrictions on Qwen3.5-VL v2 for schema/gallery surfacing, not execution behavior changes in this PR.

Overview
Documents and surfaces runtime compatibility for workflow blocks: when they fail or degrade by runtime, execution mode, or input mode, and when they are unavailable offline.

Author docs: create_workflow_block.md adds a Runtime restrictions section covering get_restrictions(), Severity.SOFT/HARD, scoping axes, shared presets, and examples—aligned with describe_interface and the execution engine.

Generated gallery: build_block_docs.py injects an optional Runtime compatibility section after Properties by calling get_air_gapped_availability() and get_restrictions() on each manifest (severity icons, scoped notes; omitted when empty). mkdocs.yml enables def_list for that layout.

Bug fix: qwen3_5vl/v2.py now declares get_restrictions() (GPU required for local CPU; hosted remote 404 when QWEN_3_5_ENABLED is false)—matching v1 behavior that v2 did not inherit.

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