feat: preserve execution ownership in sagan concentrator #1905

[svelderrainruiz]

Summary

• transplant the Sagan context concentrator onto the current 1905 host-fabric stack
• preserve execution-cell, Docker-lane, and harness ownership through subagent episode receipts and concentrator digests
• surface compact ownership labels in handoff output so execution topology survives compaction

Validation

• node --test tools/priority/tests/subagent-episode.test.mjs tools/priority/tests/subagent-episode-schema.test.mjs tools/priority/tests/sagan-context-concentrator.test.mjs tools/priority/tests/sagan-context-concentrator-schema.test.mjs tools/priority/tests/handoff-entrypoint-contract.test.mjs
• Invoke-Pester tests/Import-HandoffState.Tests.ps1 -Output Detailed
• pwsh -NoLogo -NoProfile -File tools/Test-AgentHandoffEntryPoint.ps1 -Quiet
• node tools/npm/run-script.mjs docs:manifest:validate
• node tools/priority/sagan-context-concentrator.mjs --repo-root .
• pwsh -NoLogo -NoProfile -File tools/Print-AgentHandoff.ps1 -ApplyToggles -AutoTrim
• git diff --check

[svelderrainruiz]

Stacked cleanly behind #1924.

This slice preserves execution ownership inside the concentrator:

• subagent-episode now records execution cell, Docker lane, harness instance, runtime surface, process model, and premium authorization state
• sagan-context-concentrator now carries that ownership into hot/warm memory and recent digests
• handoff rendering shows compact ownership labels directly from the concentrator receipt

Refresh note:

• the full #1921 -> #1925 chain was rebuilt on current upstream ancestry after develop absorbed the earlier governor-process-model slice
• current #1925 head is e8fbc50e
• merge admission remains armed and GitHub now sees the chain as normal in-flight BLOCKED, not stale-base DIRTY

Focused validation:

• node --test tools/priority/__tests__/subagent-episode.test.mjs tools/priority/__tests__/subagent-episode-schema.test.mjs tools/priority/__tests__/sagan-context-concentrator.test.mjs tools/priority/__tests__/sagan-context-concentrator-schema.test.mjs tools/priority/__tests__/handoff-entrypoint-contract.test.mjs
• Invoke-Pester tests/Import-HandoffState.Tests.ps1 -Output Detailed
• pwsh -NoLogo -NoProfile -File tools/Test-AgentHandoffEntryPoint.ps1 -Quiet
• node tools/npm/run-script.mjs docs:manifest:validate
• git diff --check

Merge admission receipt:

• tests/results/_agent/queue/merge-sync-1925.json

Budget hook: unavailable (cost-rollup-materialization-failed). Receipt: tests/results/_agent/cost/github-comment-budget-hook.json.