0.8.0: environment cleanup, mode-oriented examples, and Accepted project decisions

[xeonvs]

Parent

Sub-issue of #120 for the v0.8.0 public configuration and examples slice.

Scope

• remove obsolete environment semantics and document the exact supported variables, sources, requirements, defaults, and behavior
• organize examples/gitlab/ around supported toolkit modes and remove user-facing synthetic naming
• move context recipes beneath GitLab examples
• add an Accepted project decisions example and show how a later MR consumes it through bootstrap plus ocr_toolkit_evidence list/get
• remove obsolete GitLab migration prose and document current policy v1/v2 compatibility

Acceptance

• Runtime/default inventory has an exact contract test
• Removed variables are absent from supported configuration and examples
• Safe redaction sentinels remain redacted but are not presented as toolkit configuration
• Mode matrix and Accepted decisions creation/consumption walkthrough are complete
• Public documentation reflects current behavior only

Delivery remains part of Draft PR #122 and is not closed before external exact-head qualification.

[github-actions]

Stable v0.8.0 delivery is verified by immutable release asset release-receipt.json in v0.8.0 (SHA-256 1f2c06d197d78a2e1cdba7cafff0a0dd08cf67ced0f5c8ab4f833f0eb437dc6f).