Add MATLAB-Python bridge YAML files and porting instructions

Introduce four bridge YAML files (following NDI-python pattern) that map
every DID-matlab source file to its Python counterpart, tracking sync
status via matlab_last_sync_hash. Also add PORTING_INSTRUCTIONS.md with
drift-check commands, porting conventions, and current sync status.

All recent MATLAB changes (binary-mode fixes, fread/fwrite updates) were
verified to already be handled correctly by Python's Fileobj.fopen()
which appends 'b' to mode strings automatically.

https://claude.ai/code/session_015g95pQvxDUnTWxHYmTnreG

Author: claude

PORTING_INSTRUCTIONS.md

@@ -0,0 +1,187 @@
+# DID MATLAB-to-Python Porting Instructions
+
+This document describes how to keep DID-python synchronized with DID-matlab
+using the YAML bridge files.
+
+## Bridge Files
+
+The bridge files live in `src/did/` and define the contract between MATLAB and
+Python implementations:
+
+| Bridge file | Scope |
+|---|---|
+| `did_matlab_python_bridge.yaml` | Core classes: database, document, query, ido, documentservice, binarydoc |
+| `did_matlab_python_bridge_implementations.yaml` | Implementation classes: sqlitedb, doc2sql, binarydoc_matfid |
+| `did_matlab_python_bridge_file.yaml` | File I/O: fileobj, readonly_fileobj, binaryTable, utilities |
+| `did_matlab_python_bridge_util.yaml` | Utilities: databaseSummary, compareDatabaseSummary, fun, datastructures, db, common |
+
+## Checking for Drift
+
+To check whether a MATLAB file has changed since the last Python sync, use the
+`matlab_last_sync_hash` field from the bridge YAML:
+
+```bash
+# For a single file:
+git -C /path/to/DID-matlab log <matlab_last_sync_hash>..HEAD -- <matlab_path>
+
+# Example:
+git -C /path/to/DID-matlab log 205d34b..HEAD -- src/did/+did/+file/fileobj.m
+```
+
+If the command produces output, the MATLAB file has changed since the last port.
+
+### Bulk drift check
+
+Run this to check all bridge files at once:
+
+```bash
+cd /path/to/DID-matlab
+for yaml in /path/to/DID-python/src/did/did_matlab_python_bridge*.yaml; do
+    echo "=== $(basename $yaml) ==="
+    # Extract matlab_path and matlab_last_sync_hash pairs
+    python3 -c "
+import yaml, sys
+with open('$yaml') as f:
+    data = yaml.safe_load(f)
+for section in ['classes', 'functions']:
+    for item in data.get(section, []):
+        path = item.get('matlab_path', '')
+        sync_hash = item.get('matlab_last_sync_hash', '')
+        name = item.get('name', '')
+        if path and sync_hash:
+            print(f'{name}|src/did/{path}|{sync_hash}')
+" | while IFS='|' read name path hash; do
+        changes=$(git log --oneline "$hash"..HEAD -- "$path" 2>/dev/null)
+        if [ -n "$changes" ]; then
+            echo "  DRIFT: $name ($path)"
+            echo "$changes" | sed 's/^/    /'
+        fi
+    done
+done
+```
+
+## Porting a MATLAB Change to Python
+
+### Step 1: Identify the change
+
+```bash
+git -C /path/to/DID-matlab log <sync_hash>..HEAD -- src/did/<matlab_path>
+git -C /path/to/DID-matlab diff <sync_hash>..HEAD -- src/did/<matlab_path>
+```
+
+### Step 2: Locate the Python counterpart
+
+Use the bridge YAML to find `python_path` and `python_class` / `python_name`.
+
+### Step 3: Apply the change
+
+Follow these conventions when porting:
+
+| MATLAB | Python |
+|---|---|
+| `camelCase` method names | `snake_case` method names |
+| `struct` | `dict` |
+| `cell array` | `list` |
+| `char` / `string` | `str` |
+| `logical` | `bool` |
+| `[]` (empty) | `None` or `[]` depending on context |
+| `nargin`, `varargin` | `*args`, `**kwargs` |
+| `arguments` block | Type hints + validation |
+| Name-value pairs | `**kwargs` |
+| 1-based indexing | 0-based indexing |
+
+### Step 4: Update the bridge YAML
+
+After porting, update the entry in the bridge YAML:
+
+1. Set `matlab_last_sync_hash` to the current MATLAB commit hash for that file:
+   ```bash
+   git -C /path/to/DID-matlab log -1 --format="%h" -- src/did/<matlab_path>
+   ```
+2. Remove `matlab_current_hash` and `out_of_sync` / `out_of_sync_reason` if present.
+3. Update the `decision_log` with the sync date.
+
+### Step 5: Run symmetry tests
+
+```bash
+# Python tests
+pytest -m make_artifacts -v
+pytest -m read_artifacts -v
+```
+
+If MATLAB is available, run the full 3-step symmetry cycle:
+1. MATLAB `makeArtifacts` tests
+2. Python `makeArtifacts` + `readArtifacts` tests
+3. MATLAB `readArtifacts` tests
+
+## Bridge YAML Field Reference
+
+| Field | Required | Description |
+|---|---|---|
+| `name` | Yes | MATLAB function/class name |
+| `type` | Yes | `class` or `function` |
+| `matlab_path` | Yes | Path relative to `src/did/` in DID-matlab |
+| `matlab_last_sync_hash` | Yes | Short SHA of the MATLAB commit last ported to Python |
+| `matlab_current_hash` | No | Current MATLAB hash when out of sync (for tracking) |
+| `python_path` | Yes | Path relative to `src/did/` in DID-python |
+| `python_class` | If class | Python class name |
+| `python_name` | If function | Python function name |
+| `inherits_matlab` | No | MATLAB parent class(es) |
+| `inherits_python` | No | Python parent class(es) |
+| `out_of_sync` | No | `true` if MATLAB has diverged |
+| `out_of_sync_reason` | No | Human-readable explanation of the divergence |
+| `decision_log` | Yes | Sync status, dates, deviation rationale |
+| `properties` | No | List of property mappings |
+| `methods` | No | List of method mappings |
+
+## Adding a New MATLAB File
+
+When a new file is added to DID-matlab that needs a Python counterpart:
+
+1. Create the Python implementation following the conventions above.
+2. Add an entry to the appropriate bridge YAML file.
+3. Set `matlab_last_sync_hash` to the MATLAB commit that introduced the file.
+4. Run symmetry tests to verify cross-language compatibility.
+
+## Current Sync Status
+
+As of 2026-04-13, the repositories are **in sync** for all core functionality.
+
+### Recently resolved (no Python changes needed)
+The following MATLAB changes (March 29-31, 2026) were verified to already be
+handled correctly by Python:
+
+- **fileobj / readonly_fileobj / binaryTable / binarydoc_matfid**: MATLAB
+  changed default permission `'r'` -> `'rb'` for Linux binary-mode
+  compatibility. Python's `Fileobj.fopen()` already appends `'b'` to the mode
+  string if not present (line 88-89 of `file.py`), so all files are opened in
+  binary mode regardless. **Behaviorally in sync.**
+- **fileobj fread**: MATLAB changed default precision from `'char'` to
+  `'uint8'`. Python's `fread()` returns raw `bytes`, which is equivalent to
+  `uint8`. **No change needed.**
+- **fileobj fwrite**: MATLAB updated permission check to allow `'r+'` mode.
+  Python relies on native file objects to reject writes on read-only files.
+  **No change needed.**
+- **mustBeValidPermission**: MATLAB added binary-mode variants. Python's
+  `must_be_valid_permission()` already accepts `rb`, `wb`, `ab`, etc.
+  **Already in sync.**
+- **sqlitedb**: MATLAB replaced `websave` with `ndi.cloud.api.files.getFile`
+  for URL downloads. This is MATLAB-ecosystem-specific; Python uses its own
+  download mechanism. **Not applicable to Python.**
+
+## Not Yet Ported from MATLAB
+
+These MATLAB features do not yet have Python counterparts:
+
+| MATLAB feature | Bridge file | Priority |
+|---|---|---|
+| `database.freeze_branch` | bridge.yaml | Low |
+| `database.is_branch_editable` | bridge.yaml | Low |
+| `database.display_branches` | bridge.yaml | Low |
+| `database.exist_doc` | bridge.yaml | Medium |
+| `database.close_doc` | bridge.yaml | Low |
+| `document.validate` | bridge.yaml | Medium |
+| `document.dependency_value_n` | bridge.yaml | Low |
+| `document.add_dependency_value_n` | bridge.yaml | Low |
+| `document.remove_dependency_value_n` | bridge.yaml | Low |
+| `binaryTable` write methods | bridge_file.yaml | Medium |