docs(lemonade-router-builder): clarify example policies are shape references, not runnable

[AMD-melliott]

Description

Follow-up to #151. Most of that PR's feedback (Mode A trace synthetic ids,
default_used vs. rationale as the fallback signal, classifier label
mismatches scoring 0.0 silently) was already addressed by #156, which is
now merged into main.

The one piece #156 didn't cover: examples.md's bundled policies name models
a given host may not have. scripts/validate.py can't check model existence
(needs a live server), so registering one of these examples unmodified fails
at the server with 400 Collection component not registered. This documents
that the examples are shape references, not runnable as-is, and that models
should be swapped for ones the target host actually has before registering.

[sdevinenamd]

Thank you for creating this Matt!
I addressed this in #156 in a different location[skill.md] for better visibility:

SKILL.md Step 1: "A name the user did give may still not exist on the target host - the offline validator can't check that (Step 8b closes the gap)."
SKILL.md Step 8b: "ready: true from the validator only means the JSON is schema-valid - it says nothing about whether these models exist on the target host. Run #1 for every candidate/classifier model before #2, or /pull will 400 on a policy that just passed validation."

[AMD-melliott]

Thank you for creating this Matt! I addressed this in #156 in a different location[skill.md] for better visibility:

SKILL.md Step 1: "A name the user did give may still not exist on the target host - the offline validator can't check that (Step 8b closes the gap)."
SKILL.md Step 8b: "ready: true from the validator only means the JSON is schema-valid - it says nothing about whether these models exist on the target host. Run #1 for every candidate/classifier model before #2, or /pull will 400 on a policy that just passed validation."

Thanks for confirming - just didn't want this to disappear into the ether without confirmation.