[PierreRaybaut]

Lets users set the metadata expected by application plugins (exposure time, shot number…) from object titles with Edit > Metadata > Add metadata..., without writing Python.

• Optional extraction pattern (regular expression) searched in the formatted value: its first group, or the whole match, becomes the value. Objects without a match are left unchanged, unless If no match asks for an error; the preview shows them.
• Scale factor for float and integer conversions (e.g. 0.001 to convert ms to s).
• Metadata keys may now contain dots and hyphens, as plugin keys do. A Known keys list copies a key already present on the selected objects; it goes through the get_known_metadata_keys panel hook, which the plugin SDK branch will extend with keys declared by application recipes.
• Fix: adding, pasting or deleting metadata now marks the workspace as modified.

Documentation (signal/image Edit menu pages, 1.4 release notes) and French translations (UI and docs) are updated. Tests: add_metadata_unit_test.py, add_metadata_app_test.py.

Assisted-by: Claude Opus 5.5