content: Phase 5 — rich inline text via structured runs (861/861)

CtText.text may be a list of runs (text marks href); CtHeading/CtQuote rich,
CtCode verbatim. New runs.sx overrides render/markdown/text methods (byte-
identical for plain strings, opt-in). 4 modes: HTML tags / markdown / nested
SX / plain asText (drift-proof). find-replace per-run marks-preserving;
search across run boundaries; CRDT block-granularity LWW; data+wire round-trip.
Runs are a Smalltalk-renderable list (not a dict — substrate can't read dict
fields under nested render dispatch). +36 tests (44 suites). Phase 6 (char-
level inline CRDT) recorded as future.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/content/scoreboard.md

@@ -12,6 +12,7 @@ _Generated by `lib/content/conformance.sh`_
 | page | 7 | 0 | 7 |
 | page-full | 4 | 0 | 4 |
 | markdown | 20 | 0 | 20 |
+| runs | 36 | 0 | 36 |
 | text | 20 | 0 | 20 |
 | section | 25 | 0 | 25 |
 | compose | 17 | 0 | 17 |
@@ -47,4 +48,4 @@ _Generated by `lib/content/conformance.sh`_
 | md-import | 38 | 0 | 38 |
 | md-doc | 12 | 0 | 12 |
 | fed | 20 | 0 | 20 |
-| **Total** | **825** | **0** | **825** |
+| **Total** | **861** | **0** | **861** |