docs(fusion_accounting_assets): CLAUDE.md, UPGRADE_NOTES.md, README.md

Mirrors Phase 1 + 2 doc layout. CLAUDE.md captures architecture, the
7-method engine API, persisted models, controllers, OWL frontend,
performance baselines (Tasks 23 + 41 numbers), test counts (140), and
Phase 3.5 backlog. UPGRADE_NOTES.md anchors the Odoo 19 reference and
records V19 deprecations applied. README.md is the user-facing intro.

Made-with: Cursor

fusion_accounting_assets/UPGRADE_NOTES.md

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+# fusion_accounting_assets — Upgrade Notes
+
+## Odoo Version Anchor
+
+This module targets **Odoo 19.0** (community-base).
+
+Reference snapshot of Enterprise code mirrored from:
+- `account_asset` (Odoo 19.0.x)
+- Source: `/Users/gurpreet/Github/RePackaged-Odoo/accounting/account_asset/`
+
+## Cross-Version Diff Strategy
+
+When a new Odoo version ships:
+
+1. Run `check_odoo_diff.sh` (in repo root) against the new Enterprise version
+2. Note any breaking changes in `account.asset` / `account.move.line` API
+3. For mirrored OWL components, diff Enterprise's new versions against ours
+   and port material changes (signature renames, new behaviour we want to
+   inherit)
+4. Re-run the full test suite + tour tests against the new Odoo version
+5. Update this file with the new version anchor + any deviations
+
+## V19 Migration Notes (already applied)
+
+- `_sql_constraints` → `models.Constraint` (every persisted model)
+- `@api.depends('id')` → removed (none introduced)
+- `@route(type='json')` → `type='jsonrpc'` (all 8 endpoints in
+  `controllers/assets_controller.py`)
+- `numbercall` removed from `ir.cron` (data/cron.xml)
+- `res.groups.users` → `user_ids` and `ir.ui.menu.groups_id` →
+  `group_ids` (security + menu_views.xml)
+
+## Phase 3 → Phase 3.5 Migration
+
+If we ship Phase 3.5 (sub-annual depreciation frequency, disposal journal
+entries, multi-currency, allocation rules), changes will go in
+incremental commits. No DB migration needed (Phase 3 schema is
+forward-compatible — new columns will be nullable / default-valued).
+
+## Coexistence with Enterprise `account_asset`
+
+The migration step in `fusion.migration.wizard` backfills `fusion.asset`
+records from existing `account.asset` rows. It is idempotent (skips rows
+already linked via the `legacy_account_asset_id` column). Verified live
+on westin-v19: 2 records migrated cleanly.
+
+When `account_asset` is installed the Asset Management menu hides via
+`fusion_accounting_core.group_fusion_show_when_enterprise_absent`. The
+engine and AI tools remain available for chat-driven workflows.