docs: simplify agent context and resolve conflicting guidance

[thymikee]

Summary

Remove generic execution advice, basic CLI tutorials, duplicated checklists, and rhetorical explanations from contributor context. Apply the GPT-6 Astra guidance by narrowing instructions to repository-specific constraints and resolving conflicting rules.

• Align immediate skill startup with conditional help lookup, parallel work with distinct devices, and CI requirements with selected checks.
• Clarify publication authorization, dependent PR publication versus merge-readiness, and validation after rebasing.
• Correct misleading gate/sandbox failure diagnoses, nonexistent depgraph-to-gate input, and pure-test-move verification. Preserve non-obvious constraint comments.

Seven context files changed. Scope covers contributor guidance; the reviewed glossary and packaged skills remain unchanged. Compared with main, AGENTS.md shrinks from 9,994 to 7,805 bytes, and root context plus routed procedures shrink 11.7%. Existing context budgets and gate definitions are unchanged.

Validation

Validated commit: 501426464c587f4efb6ff6028ba4ffc34b99821c.

Repository formatting, diff checks, referenced local-path checks, and the required affected gate passed (all four guidance contracts). The gate ran with host process-inspection access required by its harness. Manually reviewed instruction scope and cross-file consistency against the glossary, four packaged skills, and all nine routed procedures; checked affected-selector behavior against code. Documentation only, so runtime tests do not apply. CI on the updated PR head remains authoritative.

[thymikee]

The new AGENTS.md precedence rule is unsafe: saying user instructions “take precedence over repository and skill guidance” invites agents to bypass binding repository constraints such as required gates, device/session ownership, worktree safety, and authorization boundaries.

Please narrow it: user requests define task intent and override discretionary guidance only; system/developer requirements and repository hard rules remain binding, except where a rule explicitly makes user authorization the condition for proceeding. On conflict, identify the exact constraint rather than silently bypassing it.