Add the node's function name to NodeSnapshot

[jitu5]

Description

Fixes #5653.

get_project_snapshot exposes each node's name, namespace, tags, inputs and outputs, but not the name of the underlying function. Kedro-Viz needs the function name when reading the graph from the snapshot instead of a live KedroSession (kedro-org/kedro-viz#2265):

• to reconstruct its existing node IDs, which are a hash of the node's string form (which includes the function name), avoiding a breaking change for anything keyed on those IDs

Development notes

• Added func_name: str to NodeSnapshot, populated in _node_to_snapshot from Node._func_name, the readable function name Kedro already derives internally (the same one kedro registry describe prints). The value is available at snapshot-build time, so no extra project loading is needed.
• Updated the inspection docs (NodeSnapshot field list and example) and the GET /snapshot example response in the serving docs.
• Tests: extended the NodeSnapshot instantiation and _node_to_snapshot tests, and the snapshot endpoint test now asserts func_name appears in the JSON payload.

Note on the constructor: func_name is added as a required field, second in NodeSnapshot, so it sits next to name in serialized output. This changes the signature for any code that constructs NodeSnapshot positionally, likely rare, since snapshots are produced by Kedro and all internal call sites use keyword arguments. Happy to make it keyword-only (field(kw_only=True)) or give it a default if preferred.

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Checklist

• Read the contributing guidelines
• Signed off each commit with a Developer Certificate of Origin (DCO)
• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added a description of this change in the RELEASE.md file
• Added tests to cover my changes
• Checked if this change will affect Kedro-Viz, and if so, communicated that with the Viz team

[ElenaKhaustova]

func_name inserted as a required positional field silently corrupts field values for any pre-existing positional NodeSnapshot(...) call (values shift by one field with no error). Should be field(kw_only=True) or given a default as you proposed.

[jitu5]

I’ll make func_name required but keyword-only so existing positional fields cannot silently shift.

[ElenaKhaustova]

LGTM 👍

[ravi-kumar-pilla]

LGTM 💯