feat(validation): expose strict reusable settings validators

[lmeyerov]

Problem

PlotterBase.settings(url_params=...) currently merges arbitrary keys/values into _url_params with minimal validation.

For downstream tool surfaces, we need reusable strict validation of view-setting payloads (URL params and axis/encoding-like structured settings) with explicit error messages.

Current behavior

settings() effectively does:

• res._url_params = dict(self._url_params, **url_params)

Collections have a dedicated validator path, but most settings do not.

Additional audit notes (2026-04-29)

• In Louie/GraphAgent, bad settings are often silently dropped by allowlist/type filters and only logged at debug level.
• Without a canonical strict validator from pygraphistry, downstream integrations duplicate partial checks and drift.
• Axis-related payloads (encodeAxis, ring axis configs) especially need deep, reusable validation APIs.

Requested behavior

Provide a canonical validation API for settings payloads, for example:

• strict mode that raises on invalid keys/types/ranges
• optional autofix mode for best-effort normalization
• machine-readable schema for valid key/value contracts

This could include helpers to validate:

• URL params (scalar/bool/ranged numeric where appropriate)
• React-style settings values and known complex payloads
• axis-like row structures (for encode axis payloads)

Why this matters

• Makes PyGraphistry validation reusable by downstream integrations.
• Avoids each integration duplicating ad-hoc allowlists and type checks.
• Produces clear, actionable errors for user-facing agent flows.

Related

• Deep ring axis validation: feat(gfql): deep axis payload validation for ring_*_layout calls #1239
• graphistry-js encodeAxis contract issue: feat(client-api): harden encodeAxis input validation + schema clarity graphistry-js#195