Add source callout to example walk-through docs

[chris-colinsky]

Summary

Inserts a Material !!! info "Source" admonition between the H1 and the lead paragraph on every example walk-through doc. The admonition links the page's main.py on GitHub (/blob/main/examples/<name>/main.py), opening in a new tab via {target="_blank" rel="noopener"}.

Applied uniformly to all 13 walk-throughs (one callout each): chat-with-multimodal, checkpointing-and-migration, explicit-subgraph-mapping, fan-out-with-retry, hello-world, langfuse-observability, multimodal-prompt, nested-subgraphs, observer-hooks, parallel-branches, production-observability, routing-and-subgraphs, tool-use.

Styling

• Overrides the default Material info-admonition accent to the project lavender rgb(228, 193, 249) (matching the inline-code color used elsewhere in the slate theme).
• Inside the admonition, slate-theme link color shifts to the body-text tone rgba(226, 228, 233, 0.82) so the URL reads as content rather than as a highlighted action against the lavender backdrop.

Currently !!! info is used only for these Source callouts site-wide, so the styling effectively scopes to "the Source box". If a future doc adds a non-Source info admonition that should stay default-blue, the convention can flip to a custom !!! source type and the CSS re-scope to .admonition.source. Comment in extra.css notes this.

URLs

Uses the LunarCommand org for now per the project_org_move_to_openarmature memory; will need a one-line perl substitution after the OpenArmature org move.

Test plan

• uv run mkdocs build --strict clean
• Headless Chromium preview of the rendered callout in slate theme (link color reads as muted gray on lavender background)
• All 13 walk-through pages have the callout inserted at the same position (between H1 and lead paragraph)
• Spot-check one of the GitHub links opens in a new tab and lands on the right main.py

[Copilot]

Pull request overview

Adds a consistent “Source” callout to each example walk-through doc, linking directly to the corresponding examples/<name>/main.py on GitHub, and introduces scoped styling so the callout matches the site’s slate-theme visual language.

Changes:

• Inserted a !!! info "Source" admonition between the H1 and lead paragraph across 13 example walk-through pages, linking to the example’s main.py (opens in a new tab with rel="noopener").
• Added CSS overrides to restyle Material’s info admonition accent to the project lavender, plus a slate-theme link color adjustment within that admonition.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
docs/stylesheets/extra.css	Adds styling overrides for the Source callout (info admonition) and link color within it (slate scheme).
docs/examples/chat-with-multimodal.md	Adds “Source” admonition linking to examples/chat-with-multimodal/main.py.
docs/examples/checkpointing-and-migration.md	Adds “Source” admonition linking to examples/checkpointing-and-migration/main.py.
docs/examples/explicit-subgraph-mapping.md	Adds “Source” admonition linking to examples/explicit-subgraph-mapping/main.py.
docs/examples/fan-out-with-retry.md	Adds “Source” admonition linking to examples/fan-out-with-retry/main.py.
docs/examples/hello-world.md	Adds “Source” admonition linking to examples/hello-world/main.py.
docs/examples/langfuse-observability.md	Adds “Source” admonition linking to examples/langfuse-observability/main.py.
docs/examples/multimodal-prompt.md	Adds “Source” admonition linking to examples/multimodal-prompt/main.py.
docs/examples/nested-subgraphs.md	Adds “Source” admonition linking to examples/nested-subgraphs/main.py.
docs/examples/observer-hooks.md	Adds “Source” admonition linking to examples/observer-hooks/main.py.
docs/examples/parallel-branches.md	Adds “Source” admonition linking to examples/parallel-branches/main.py.
docs/examples/production-observability.md	Adds “Source” admonition linking to examples/production-observability/main.py.
docs/examples/routing-and-subgraphs.md	Adds “Source” admonition linking to examples/routing-and-subgraphs/main.py.
docs/examples/tool-use.md	Adds “Source” admonition linking to examples/tool-use/main.py.

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