First implementation (#1)

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spec/09-figures-tables-equations.md

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+# 9. Figures, tables and equations
+
+## 9.1 Figures and panels
+
+A figure holds its panels, its caption and its notes.
+A panel's own content is its label only.
+Its image and region are evidence, not content: re-extracting the image at native resolution adds an asset and changes no hash.
+
+| Panel attribute | Holds |
+| --- | --- |
+| `image` | `{sha256, media_type, native, dpi?}`: the embedded image, at native resolution when the PDF holds one. |
+| `crop` | `{sha256, media_type, dpi}`: a crop of the panel's region at a fixed resolution. |
+| `figure_text` | `[{id, text, role, page_fp?, boxes?}]`: text found inside the panel, with `role` `axis-label`, `tick-label`, `legend`, `annotation` or `other`. |
+
+Text inside a figure is not prose and is not split into sentences.
+Its items have IDs ([4.2](04-identity.md#42-minting-node-ids)) so that a digitization can anchor its axis labels to them.
+A panel's region on the page is its location ([7.4](07-geometry.md#74-locationsjsonl)).
+
+## 9.2 Tables
+
+A table holds its caption, an optional head, one body and its notes.
+Rows and cells are nodes, with all five values, so the gate, the hashes and the database treat them like any other node, and a cell is addressed like a sentence.
+
+Columns are defined in the table's `columns` attribute, each with an ID and a header path: the IDs of the header cells above it, outermost first.
+Header text is stored once, in the header cells.
+A row's `header_path` lists the cells that label it: a row-group header and the row's own header cell.
+A cell records its column, its spans and its role; the expanded grid is derived, never stored.
+
+So inserting a row that a reading dropped adds a row node and changes no other row's or cell's ID or hash, and fixing a header cell changes that cell, not the table.
+A table continued across pages is one table node; its pages are locations.
+For people, a cell can be shown as "Table 2, row CT–CT, column K_r" from its header paths.
+
+## 9.3 Equations
+
+An equation keeps its source as written, `tex` from a conversion or `typst` from a draft, and its printed number as its `label`, so numbering never collides with a renderer's own.
+An equation that the source numbers line by line (Eq. 3a) has `equation-line` children, each with its own label and source.
+MathML is derived by a pinned tool and recorded, with the tool's name and version, in `derived/mathml.jsonl`.