docs(k3): round 19, a document's own identity, per-run frontmatter, and a description from the source

The report for K3-19, measured from a frozen export of 77e7cab: R761 from the
base 56b00e7 against 77e7cab -- directory `14ce59dc-...` -> `r761-prosesskoden`,
2 761 concepts and 710 shells unchanged, 110 = 110, 1 807 descriptions, the
flagged edition and address on 2 761 of 2 761, hit@1/8/50 over S1-S6 6/6 at
both k, `okf check` 4 of 4 with 0 findings, and --ingested-at alone
confirmed on 2 761 of 2 761.

Reported first rather than repaired: the known-positive falls from rank 1 to
not delivered at the default k (13 at k = 50), decomposed to the directory
name alone; and the order's own `sources` value is refused by PyYAML on every
concept while `okf check` accepts it.

CHANGELOG under [Unreleased], the README and CLAUDE.md paragraphs carry the
final numbers, and the README test count moves to 1659 collected.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,65 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- **A NISO-STS document's own identity names its directory and titles its
+  `sources` entry (K3-19).** `okf build` put every concept of an STS delivery
+  under a directory named for the delivery file -- measured, a UUID occurring
+  0 times in the document -- while the document's one `<std-ident>` carried a
+  `<doc-number>`. `extract.declared_identity` reads exactly one `<std-ident>`
+  (`<doc-number>`, `<year>`) and exactly one `<title-wrap>`; a value stated
+  more than once is not read. The directory is the `<doc-number>` through the
+  id grammar, replacing only the file's stem, and `sources[0].title` is
+  `<doc-number>` + `<year>`, then the `<title-wrap>` title, then the file name
+  -- the first that can be written into the flow mapping verbatim (the
+  measured `<full>` carries commas, so it never is). A declared name two
+  documents in one run claim is used by neither, and stderr says so.
+  - **Consumer cost: a re-run, and an STS document's concept ids move**
+    (`<uuid>/...` -> `<doc-number>/...`). Every other file type is untouched:
+    the five-document folder rebuilds identical except the `log.md` line that
+    records the venv's converter path.
+  - **Measured side effect on ranking, reported rather than repaired:** hit@1
+    / 8 / 50 over S1-S6 stays 6/6 at both `k`, but the known-positive falls
+    from rank 1 to not delivered at the default `k` (13 at `k` = 50).
+    `consume`'s first signal reads a concept id's segments, and on a
+    one-document bundle every id now carries the document's own name; renaming
+    only the directory back restores rank 1. `--rarity-weight` delivers it at
+    rank 4 with S1-S6 unmoved, and stays off.
+
+### Added
+
+- **`okf build --frontmatter KEY=VALUE`**, repeatable, stamps a key on every
+  concept of a run -- for what an operator knows and a document does not say,
+  such as an edition or a publisher's address. SPEC SS 4.1 "Extensions" lets
+  a producer add any key; SS 11 forbids a consumer to reject one. Split on the
+  FIRST `=`, and the value is written verbatim on ONE line, because this
+  package's readers are line-oriented and blind to a block-form `sources`.
+  Precedence: a stated value beats what the document declares, which beats the
+  file name. A run may add any key and REPLACE only `sources` and
+  `description`; every key the door writes itself -- including Door A's
+  `ingest_manifest`, which would make that door claim the file -- is refused
+  before a proposal is written (`run_frontmatter_invalid`), as is a value that
+  would not read back as stated. Reachable as `build(frontmatter=...)` and as a
+  keyword-only `concept_frontmatter_values` on `measure`, `process_inbox` and
+  `render_inbox_concept`. Without the flag nothing moves. **Note:** a
+  `sources` value carrying a URL or `X:Y` in the flow mapping passes `okf
+  check` and is refused by PyYAML's `safe_load` -- measured on 2 761 of 2 761
+  concepts with such a value -- and it is written verbatim as stated.
+- **`description` for an STS section, from its own first spec point.** The
+  first `<p>` of the first direct-child `<sec sec-type="spec">`, whole,
+  carried by the plan entry, screened by the gate, and written only where a
+  YAML reader reads it verbatim (`inbox._yaml_plain`; over 2 024 measured
+  values the rule and PyYAML agree on every one). The spec sets no length, so
+  the one-paragraph limit is ours. On the measured document: 2 026 of 2 761
+  titled sections carry a spec point, 1 807 descriptions are written (2 points
+  have no `<p>`, 217 carry `": "`), none is invented, and none is derived from
+  a title.
+
+`--ingested-at` alone was confirmed to stamp every concept, on the segmented
+route too, and to date `log.md`: 2 761 of 2 761. Report:
+[`docs/2026-09-11-k3-runde19-dokumentidentitet-og-frontmatter.md`](docs/2026-09-11-k3-runde19-dokumentidentitet-og-frontmatter.md).
+
 ## [0.8.2] — 2026-09-11
 
 ### Added