Document Linear Excel integration

docs/project-history-and-external-model-architecture.md

@@ -9,7 +9,8 @@ This document records architectural direction for future work. It is not a final
 - persist undo/redo across page reloads and application restarts
 - provide a project-wide version history with named restore points
 - preserve an auditable sequence of user, import, migration and restore operations
-- support future Revit/CSV round-trips using stable IFCGUID-based links
+- support the Revit/Linear-XLSX round-trip using stable, exact
+  Worksharing-ID-based external identity
 - keep the persistence boundary replaceable so PostgreSQL can be adopted later
 
 ## Separate Concerns
@@ -111,11 +112,12 @@ Implemented automatic-snapshot policy:
 - automatic capture and retention run inside the same transaction as the
   triggering project revision
 
-## Revit / CSV / IFCGUID Round-Trip Direction
+## Revit / Linear Excel Round-Trip Direction
 
-**Deferred:** further Revit work will be tackled later, then through the
-CSV export/import of the Linear plugin in Revit instead of Dynamo. Details:
-[Revit-CSV requirements, section 1](spec/revit-csv-integration-requirements.md).
+Phase 14 is active and follows the
+[Linear-Excel requirements](spec/revit-excel-integration-requirements.md) and
+[R0–R10 plan](spec/revit-excel-phase-14-plan.md). The existing CSV/IFCGUID
+runtime is a legacy starting point for the cutover, not the target model.
 
 External model exchange should use explicit staging and link entities instead of writing imported rows directly into circuits.
 
@@ -124,9 +126,12 @@ Conceptual entities:
 - `ExternalModelSource`
   - identifies a Revit/IFC model or another external source within a project
 - `ExternalImportBatch`
-  - file name, checksum, import time, format/version and processing status
+  - file name, checksum, import time, object count and processing status
+  - only the latest batch keeps original workbook bytes, matrix and the
+    configuration copy; older batches keep date, filename, checksum and count
 - `ExternalModelObject`
-  - stable IFCGUID and optional Revit element identifiers
+  - exact case-sensitive Worksharing-ID as external identity
+  - optional IfcGUID as non-unique source redundancy
   - source attributes and last-seen import batch
 - `ExternalObjectLink`
   - explicit relationship to a project device, circuit device row or another future domain entity
@@ -137,13 +142,27 @@ Conceptual entities:
 
 Required behavior:
 
-- IFCGUID uniqueness is scoped to project and external model source.
+- Worksharing-ID uniqueness is scoped to the external source and uses exact,
+  case-sensitive comparison. IfcGUID is not a matching key.
 - Parsing writes to staging first.
 - Users preview additions, changes, missing objects and conflicts before applying them.
 - Applying an import creates one project revision and one auditable change set.
 - Imported source values and locally assigned planning values remain distinguishable.
-- Export retains IFCGUID and source identifiers so Revit parameters can be matched deterministically.
-- Missing objects and duplicate/conflicting identifiers are reported, never silently reassigned.
+- Export retains Worksharing-ID so Linear can match rows deterministically.
+- Missing objects and duplicate/conflicting Worksharing-IDs are reported,
+  never silently reassigned.
+
+The project configuration has no separate revision counter. Stateless plans
+and apply requests bind to `expectedRevision`; every applied import batch holds
+its configuration copy. Apply reparses the retransmitted workbook. Undo and
+Redo operate only on persisted complete before/after states and never parse an
+Excel file.
+
+Deleting a linked row, circuit or group detaches affected Revit objects in the
+same typed command after an explicit warning; its inverse restores all links.
+Only deleting referenced rooms and distribution boards is blocked. Linked
+objects always derive their board from their row, while a room default-board
+change affects only unassigned objects.
 
 ## SQLite and PostgreSQL Direction
 
@@ -292,7 +311,8 @@ Remaining constraints before completing project version history:
   boundary; extend it whenever further project mutations are introduced
 - project creation remains initialization at revision zero, while global device
   templates remain outside any single project history
-- do not model IFCGUID as an overloaded circuit equipment identifier
+- do not model Worksharing-ID or IfcGUID as an overloaded circuit equipment
+  identifier or an internal relation id
 - keep database backup/restore checks separate from project history tests
 
 ## Deferred Decisions
@@ -300,5 +320,6 @@ Remaining constraints before completing project version history:
 - whether large snapshot payloads remain in PostgreSQL or move to object storage
 - branch visualization after undo followed by new edits
 - user/role model and actor attribution
-- supported Revit CSV dialects and parameter mapping UI
+- Linear-XLSX compatibility beyond the observed sample and any future
+  project-independent mapping profiles
 - PostgreSQL deployment topology and migration date