[JSdotNet]

Summary

Devbook 1.16.0 (contract 25) adds a sync field: which way changes flow between a unit and its code — push, pull, sync, report or off — stated on a folder overview, a context.md, a context page or a unit's root chapter, and resolved nearest-wins (unit → page → context → folder → report). This PR lets Backlog read it, store it, show it beside each block's status in the Devbook panes, and edit it.

Changes

• Database — node.sync and chapter.sync (schema v4), written identically by tools/devbook/build-database.mjs and DevbookDatabaseBuilder; the parity fixture now carries sync values so the new columns are compared.
• Schema and findings — sync is a known field on MetadataRecord; DevbookSchema.SyncValues; DevbookMetadataFindings reports a value outside the five, and a block that is no sync level (an owned chapter, a requirements/invariants page, tech/ai), mirroring the checker's syncIssues.
• DevbookSync — places a block (level or refusal) and resolves a unit's direction with the level it came from.
• UI — DevbookSyncSelector beside the status in MetadataView: a picker whose empty entry inherits and names its source ("sync push · from context"), a badge on a read-only branch, the bare word where nothing places the block. Panes cascade a DevbookSyncScope; MetadataFileView draws a file's headline when its block takes a direction even if it states nothing else (the building block view's empty fence).
• Writing — DevbookMarkdownSyncWriter beside DevbookMarkdownStatusWriter, through DevbookWriteGuard.WritablePath; refuses a value or a block the rule refuses. DevbookSyncReading reads a document plus its context and folder overview once per chapter load. Domain, arc42 and design panes wired.
• Storybook — "The sync direction, beside the status" on devbook/state.
• Devbook vendoring — the 1.16.0 tools/rules/stamp; identical to what Name each domain event's raiser and adopt devbook 1.16.0 #937 landed on main meanwhile, so it merges as a no-op.

Testing

• CI build (Backlog.WithoutAppHeads.slnf, Release, warnings as errors): clean. Full suite: 10830 passed, 0 failed, 1 skipped (E2E needs a live AppHost). Parity tests pass; re-run after merging main.
• New: DevbookSyncTests (placement matrix, nearest-wins, findings, rule-text pin against .agents/rules/devbook-chapter-metadata.md), DevbookSyncSelectorTests, DevbookSyncWriteTests (writer + reading across files), a domain-pane and an arc42-pane test.
• Playwright QA with Aspire monitoring: domain units/pages/context map, cascade and write/clear, arc42 building block view, design components, tech/ai show none, Storybook story. Two first-pass findings — same-page units not refreshed after a file-level pick, and no picker on an empty file block — fixed and re-validated. Logs: only an unrelated sync startup timeout.
• node .devbook/_tools/devbook-meta/build.mjs --check passes; check-metadata.mjs 0 blocking.

Verification — spec verdicts

Against the plan item and devbook 1.16.0's "Sync direction" rule (.agents/rules/devbook-chapter-metadata.md).

Item	Verdict	Evidence / what it calls for
sync known in DevbookSchema, DevbookMetadataFindings, devbook-schema.sql, build-database.mjs, DevbookDatabaseBuilder	aligned	DevbookSyncTests, DevbookBuilderParityTests (fixture carries sync)
Levels and refusals (folder / context / page / unit; owned chapters and pages, tech/ai refused)	aligned	DevbookSyncTests placement matrix; rule-text pin of directions, default, unit/owned types, overview files, page bases
Nearest-wins with the level it came from, report default, unknown value skipped	aligned	DevbookSyncTests, DevbookSyncWriteTests (reading across files)
Shown beside status on each unit in the devbook panes	aligned	Playwright QA (domain, arc42, design; tech/ai none); domain-pane and arc42-pane bUnit tests
Picker writes through a writer beside the status writer, under DevbookWriteGuard, only where allowed	aligned	DevbookSyncWriteTests (refusals leave the file untouched), QA write/clear scenarios
Picker in the domain pane's context/document action bar	spec-ahead (minor)	Not built — only the open file view carries it; new work if wanted
Backlog's own devbook describing the field's UI and storage	code-ahead	Chapter change for a flow-spec session (the plan item's last step)

Unverified scenarios: none — the item carries no #### Scenario: cases.

Related

Backlog plan item backlog-sync-field of plan devbook-sync-sweeps (after units-tool, JSdotNet/devbook#208). No GitHub issue.

Not in this PR: the domain pane's context/document action bar has no sync picker (the open file view has it), and Backlog's own devbook chapters for this feature are a follow-up flow-spec session.

Checklist

• Scope is focused and excludes unrelated changes
• Documentation or instruction files were updated when governance or behavior changed — devbook chapters follow in a separate session
• Running Aspire instances for this checkout were stopped before PR creation
• Follow-up work is captured when the implementation is intentionally partial
• Issues this PR closes are linked with a closing keyword, or there are none

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