Add durable context and bounded handoff rules

[xeonvs]

Problem and resulting behavior

Long tool outputs and full conversation history can crowd the root agent's context, while loosely scoped worker handoffs can duplicate discovery or lose decisions. This release makes the root keep a compact working representation, stores durable task knowledge in repository owners, and gives bounded workers self-contained packets with accessible evidence and compact returns.

Predictable tool-heavy stages now prefer existing pipelines, scripts, repository helpers, native batching, or eligible PTC. Context recovery starts from PLANS.md, current repository state, and relevant durable artifacts instead of reconstructing the execution transcript.

The behavior is applied both to this project's own routing and to generated target instructions, project principles, and optional agent templates. Known pristine 0.9.5 templates migrate automatically; customized owners remain protected for semantic review.

Validation

• Focused orchestration, planning, and target-upgrade scenarios passed.
• Prior-pristine migration covers all four rendered AGENTS layouts and a customized-owner case.
• Full maintainer gate passed 9/9 stages, including all tests and package parity.
• Independent semantic review found no material defect; its migration-coverage concern was fixed.
• Codex plugin/skill validation and Claude plugin/marketplace validation passed.
• Claude tag dry-run and pre-push public-tree plus redacted tree/history secret scans passed.

Prepares engineering-workflow 0.9.6. No dependency on codex-orchestration or a provider-specific agent API is added.