api: add clear route settings and developer guidance

[Raphjacksun7]

Purpose

Give Python developers clear names for route media, delivery behavior, and route observations while preserving every 0.1.x import and keyword. Keep concise Connector authoring as the normal integration experience.

Staff review

1. Files changed: Python graph, Session, Connector, Endpoint, Operator, signal, and observation APIs; tests; release notes; and developer documentation.
2. Product proof enabled: application and microphone stems can choose route settings, send through Connectors, and inspect delivery without learning compiler-oriented edge vocabulary.
3. Architecture affected: Python configuration and observation APIs over the existing native Session; no second queue, graph, media engine, or provider implementation.
4. Tests and evidence: 274 Python tests pass with 29 platform skips; Ruff, formatting, strict MyPy, wheel and source builds, clean installed wheel/source consumers, Markdown links, and native tests pass.
5. Remaining scaffold/mock/loopback behavior: none introduced.
6. Scaffold inventory: n/a.
7. CODE_PROTOCOL checks: public docs use RouteSettings, DeliveryPolicy, RouteDeliveryMetrics, SignalQueueMetrics, and RouteLatencyMeasurement. EdgeContract and edge= remain tested compatibility forms.
8. Decision: PASS after required CI succeeds.