Improve joint-fit support and add parameter-evolution plotting

.github/copilot-instructions.md

@@ -100,6 +100,13 @@
   case.
 - Don't add dependencies without asking.
 
+## Tutorials
+
+- Jupyter notebooks (`docs/docs/tutorials/*.ipynb`) are **generated
+  artifacts** — never edit them by hand. Edit only the corresponding
+  `*.py` script, then run `pixi run notebook-convert` followed by
+  `pixi run notebook-prepare` to regenerate the notebook.
+
 ## Changes
 
 - Before implementing any structural or design change (new categories,

docs/architecture/architecture.md

@@ -727,6 +727,12 @@ project_dir/
 
 All examples below are drawn from the actual tutorials (`tutorials/`).
 
+> **Notebook workflow:** Jupyter notebooks (`*.ipynb`) in
+> `docs/docs/tutorials/` are generated artifacts. Edit only the
+> corresponding `*.py` script, then run `pixi run notebook-convert`
+> followed by `pixi run notebook-prepare` to regenerate the notebook.
+> Never edit `*.ipynb` files by hand.
+
 ### 8.1 Project Setup
 
 ```python

docs/docs/tutorials/ed-13.ipynb

@@ -396,7 +396,7 @@
     "TOF, respectively.\n",
     "\n",
     "You can set them manually, but it is more convenient to use the\n",
-    "`get_value_from_xye_header` function from the EasyDiffraction library."
+    "`extract_metadata` function from the EasyDiffraction library."
    ]
   },
   {
@@ -420,11 +420,11 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "project_1.experiments['sim_si'].instrument.setup_twotheta_bank = ed.get_value_from_xye_header(\n",
-    "    si_xye_path, 'two_theta'\n",
+    "project_1.experiments['sim_si'].instrument.setup_twotheta_bank = ed.extract_metadata(\n",
+    "    si_xye_path, r'two_theta\\s*=\\s*([-+]?\\d*\\.?\\d+(?:[eE][-+]?\\d+)?)'\n",
     ")\n",
-    "project_1.experiments['sim_si'].instrument.calib_d_to_tof_linear = ed.get_value_from_xye_header(\n",
-    "    si_xye_path, 'DIFC'\n",
+    "project_1.experiments['sim_si'].instrument.calib_d_to_tof_linear = ed.extract_metadata(\n",
+    "    si_xye_path, r'DIFC\\s*=\\s*([-+]?\\d*\\.?\\d+(?:[eE][-+]?\\d+)?)'\n",
     ")"
    ]
   },
@@ -1485,11 +1485,11 @@
    },
    "outputs": [],
    "source": [
-    "project_2.experiments['sim_lbco'].instrument.setup_twotheta_bank = ed.get_value_from_xye_header(\n",
-    "    lbco_xye_path, 'two_theta'\n",
+    "project_2.experiments['sim_lbco'].instrument.setup_twotheta_bank = ed.extract_metadata(\n",
+    "    lbco_xye_path, r'two_theta\\s*=\\s*([-+]?\\d*\\.?\\d+(?:[eE][-+]?\\d+)?)'\n",
     ")\n",
-    "project_2.experiments['sim_lbco'].instrument.calib_d_to_tof_linear = ed.get_value_from_xye_header(\n",
-    "    lbco_xye_path, 'DIFC'\n",
+    "project_2.experiments['sim_lbco'].instrument.calib_d_to_tof_linear = ed.extract_metadata(\n",
+    "    lbco_xye_path, r'DIFC\\s*=\\s*([-+]?\\d*\\.?\\d+(?:[eE][-+]?\\d+)?)'\n",
     ")"
    ]
   },

docs/docs/tutorials/ed-13.py

@@ -212,19 +212,19 @@
 # TOF, respectively.
 #
 # You can set them manually, but it is more convenient to use the
-# `get_value_from_xye_header` function from the EasyDiffraction library.
+# `extract_metadata` function from the EasyDiffraction library.
 
 # %% [markdown] tags=["doc-link"]
 # 📖 See
 # [documentation](https://docs.easydiffraction.org/lib/user-guide/analysis-workflow/experiment/#instrument-category)
 # for more details about the instrument parameters.
 
 # %%
-project_1.experiments['sim_si'].instrument.setup_twotheta_bank = ed.get_value_from_xye_header(
-    si_xye_path, 'two_theta'
+project_1.experiments['sim_si'].instrument.setup_twotheta_bank = ed.extract_metadata(
+    si_xye_path, r'two_theta\s*=\s*([-+]?\d*\.?\d+(?:[eE][-+]?\d+)?)'
 )
-project_1.experiments['sim_si'].instrument.calib_d_to_tof_linear = ed.get_value_from_xye_header(
-    si_xye_path, 'DIFC'
+project_1.experiments['sim_si'].instrument.calib_d_to_tof_linear = ed.extract_metadata(
+    si_xye_path, r'DIFC\s*=\s*([-+]?\d*\.?\d+(?:[eE][-+]?\d+)?)'
 )
 
 # %% [markdown]
@@ -804,11 +804,11 @@
 # **Solution:**
 
 # %% tags=["solution", "hide-input"]
-project_2.experiments['sim_lbco'].instrument.setup_twotheta_bank = ed.get_value_from_xye_header(
-    lbco_xye_path, 'two_theta'
+project_2.experiments['sim_lbco'].instrument.setup_twotheta_bank = ed.extract_metadata(
+    lbco_xye_path, r'two_theta\s*=\s*([-+]?\d*\.?\d+(?:[eE][-+]?\d+)?)'
 )
-project_2.experiments['sim_lbco'].instrument.calib_d_to_tof_linear = ed.get_value_from_xye_header(
-    lbco_xye_path, 'DIFC'
+project_2.experiments['sim_lbco'].instrument.calib_d_to_tof_linear = ed.extract_metadata(
+    lbco_xye_path, r'DIFC\s*=\s*([-+]?\d*\.?\d+(?:[eE][-+]?\d+)?)'
 )
 
 # %% [markdown]