Add source callout to example walk-through docs

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 the LunarCommand GitHub
repo (``/blob/main/examples/<name>/main.py``), opening in a new
tab via ``{target="_blank" rel="noopener"}``.

Applied 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)); inside the
admonition, slate-theme link color shifts to the body-text gray
(rgba(226, 228, 233, 0.82)) so the URL reads as content rather
than as a highlighted action against the lavender backdrop.

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

Author: chris-colinsky

docs/examples/chat-with-multimodal.md

@@ -1,5 +1,8 @@
 # Chat with multi-turn memory and a multimodal turn
 
+!!! info "Source"
+    [https://github.com/LunarCommand/openarmature-python/blob/main/examples/chat-with-multimodal/main.py](https://github.com/LunarCommand/openarmature-python/blob/main/examples/chat-with-multimodal/main.py){target="_blank" rel="noopener"}
+
 A lunar-mission Q&A assistant that maintains conversation context
 across four turns. One mid-conversation turn includes an attached
 photograph (Apollo 16 Lunar Module "Orion" on the lunar surface):

docs/examples/checkpointing-and-migration.md

@@ -1,5 +1,8 @@
 # Checkpointing and migration
 
+!!! info "Source"
+    [https://github.com/LunarCommand/openarmature-python/blob/main/examples/checkpointing-and-migration/main.py](https://github.com/LunarCommand/openarmature-python/blob/main/examples/checkpointing-and-migration/main.py){target="_blank" rel="noopener"}
+
 A lunar-mission planning pipeline that writes a SQLite checkpoint
 after every step, survives a simulated mid-pipeline crash, and then
 resumes the saved invocation under an upgraded state schema with a

docs/examples/explicit-subgraph-mapping.md

@@ -1,5 +1,8 @@
 # Explicit subgraph mapping
 
+!!! info "Source"
+    [https://github.com/LunarCommand/openarmature-python/blob/main/examples/explicit-subgraph-mapping/main.py](https://github.com/LunarCommand/openarmature-python/blob/main/examples/explicit-subgraph-mapping/main.py){target="_blank" rel="noopener"}
+
 Compare two topics by running the *same* compiled analysis subgraph
 on each, with each call site writing into disjoint parent fields.
 This is the canonical use of `ExplicitMapping`.

docs/examples/fan-out-with-retry.md

@@ -1,5 +1,8 @@
 # Fan-out with retry
 
+!!! info "Source"
+    [https://github.com/LunarCommand/openarmature-python/blob/main/examples/fan-out-with-retry/main.py](https://github.com/LunarCommand/openarmature-python/blob/main/examples/fan-out-with-retry/main.py){target="_blank" rel="noopener"}
+
 Summarize a batch of lunar-mission headlines in parallel, with
 per-headline retry and timing middleware wrapping each instance's
 subgraph run.

docs/examples/hello-world.md

@@ -1,5 +1,8 @@
 # Hello, world
 
+!!! info "Source"
+    [https://github.com/LunarCommand/openarmature-python/blob/main/examples/hello-world/main.py](https://github.com/LunarCommand/openarmature-python/blob/main/examples/hello-world/main.py){target="_blank" rel="noopener"}
+
 The smallest possible LLM-routed pipeline: classify a query, then
 either plan research on it or summarize it in one sentence. Sets the
 shape every other example builds on.

docs/examples/langfuse-observability.md

@@ -1,5 +1,8 @@
 # Langfuse observability
 
+!!! info "Source"
+    [https://github.com/LunarCommand/openarmature-python/blob/main/examples/langfuse-observability/main.py](https://github.com/LunarCommand/openarmature-python/blob/main/examples/langfuse-observability/main.py){target="_blank" rel="noopener"}
+
 Send LLM call observability to Langfuse natively: Trace at the top,
 Span observations for graph nodes, Generation observations with input,
 output, token usage, model parameters, and a native link back to the

docs/examples/multimodal-prompt.md

@@ -1,5 +1,8 @@
 # Multimodal prompt
 
+!!! info "Source"
+    [https://github.com/LunarCommand/openarmature-python/blob/main/examples/multimodal-prompt/main.py](https://github.com/LunarCommand/openarmature-python/blob/main/examples/multimodal-prompt/main.py){target="_blank" rel="noopener"}
+
 Two independent analyses of a lunar-mission photograph using
 versioned prompt templates, a fallback prompt backend, and a
 multimodal user message that carries both text and image.

docs/examples/nested-subgraphs.md

@@ -1,5 +1,8 @@
 # Nested subgraphs
 
+!!! info "Source"
+    [https://github.com/LunarCommand/openarmature-python/blob/main/examples/nested-subgraphs/main.py](https://github.com/LunarCommand/openarmature-python/blob/main/examples/nested-subgraphs/main.py){target="_blank" rel="noopener"}
+
 Question answering against a tiny baked-in document corpus, with
 two levels of subgraph nesting: outer coordinator, middle doc-QA,
 inner section-extract.

docs/examples/observer-hooks.md

@@ -1,5 +1,8 @@
 # Observer hooks
 
+!!! info "Source"
+    [https://github.com/LunarCommand/openarmature-python/blob/main/examples/observer-hooks/main.py](https://github.com/LunarCommand/openarmature-python/blob/main/examples/observer-hooks/main.py){target="_blank" rel="noopener"}
+
 Add observability to a `draft → review → finalize` pipeline without
 touching any node code. Three observer flavors run side-by-side: a
 console tracer, a per-invocation metrics collector, and the

docs/examples/parallel-branches.md

@@ -1,5 +1,8 @@
 # Parallel branches
 
+!!! info "Source"
+    [https://github.com/LunarCommand/openarmature-python/blob/main/examples/parallel-branches/main.py](https://github.com/LunarCommand/openarmature-python/blob/main/examples/parallel-branches/main.py){target="_blank" rel="noopener"}
+
 Enrich a lunar-mission news article with three independent
 analyses (one-sentence summary, sentiment label, topic tags)
 running concurrently as separate subgraphs.