feat: comment categories; emend, relink and resolve corrections

scienting-layer/1: an optional, fixed category on comment, caveat and
question bodies (comment, context, critique, question, correction,
feedback, resource).

Corrections: emend fixes the authors' own slip and keeps what was printed
(a run's printed), never lowering fidelity or a witness match; relink sets
or removes what a citation names; resolve sets a reference's resolution.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017R7sgDNvUGWY2zFPCq2JH6

spec/03-nodes.md

@@ -112,7 +112,10 @@ No other kind carries `attrs`, and each kind carries only its own attributes.
 | `link` | `url`, `text`. | The text. |
 | `equation` | `node`: the ID of an equation child of the sentence. | `$$` + that equation's source + `$$` |
 
-Runs are canonical: no `text` run is empty, and no two adjacent `text` runs have the same style list.
+A `text`, `link`, `cite`, `xref` or `fnmark` run MAY carry `printed`: its text as the paper prints it, where an `emend` corrected the authors ([11.6](11-corrections.md#116-emendations)).
+The run's `text` is then the emended text, and only an emend writes `printed`.
+
+Runs are canonical: no `text` run is empty, no two adjacent `text` runs have the same style list unless one of them carries `printed`, and no run's `printed` equals its `text`.
 A sentence's `equation` runs name its `equation` children, each once, in the children's order, and a sentence has no other children.
 A display equation the sentence runs through is thus part of the sentence, while keeping its own ID and hashes.
 
@@ -125,3 +128,8 @@ That of any other node is the plain projections of its text leaves joined with o
 A node's text leaves are found by walking its subtree in document order and stopping at `sentence`, `cell`, `reference`, `authors`, `keywords`, `code` and `algorithm` nodes, and at `equation` nodes whose parent is not a sentence; an `equation-line` is never a text leaf.
 
 Offsets, quotations and the text hash are all defined on the plain projection as stored, before normalization.
+
+A node's runs as printed are its runs with each run's `printed` in place of its `text`, and each `text` run that carried one joined with the adjacent `text` runs of the same style list, as the run was before an emend split it.
+Its projection as printed is the plain projection of its runs as printed; an equation's or a verbatim node's is its plain projection, and any other node's joins its text leaves' projections as printed with one U+0020.
+It is the text a witness of the paper holds, recovered from `nodes.jsonl` alone; for a node no emend touched it is the plain projection.
+The strict and lossy projections are taken over the runs as printed ([5.3](05-hashes.md#53-the-strict-projection)), and `projections.jsonl` gives an emended sentence's projections with its projection as printed.