fix(tokens): refresh stale "Opus 4.7" framing to model-neutral + Opus 4.8 anchor

Fase 4 token-opt, Item 1 of gap-review NEXT STEP #2. The prompt-cache pattern corpus + TOK scanner were frozen at an "Opus 4.7" framing after CC shipped Opus 4.8 (default, 2.1.154) and Fable 5 (2.1.170). Model-era facts re-verified against the official changelog cache before editing.

The patterns are properties of prompt-caching, not of any model, so mechanic text is now model-neutral with a single "current default: Opus 4.8" anchor — preventing a re-freeze at the next model bump.

- rename knowledge/opus-4.7-patterns.md -> prompt-cache-patterns.md (git mv, history preserved); 6 reference sites updated
- TOK scanner: line-318 finding text (human-facing) made model-neutral; header + cache-prefix-scanner + CLI comments refreshed
- configuration-best-practices.md body + footnote 4.7 -> 4.8
- human-facing docs: commands/{tokens,help,manifest}.md, project CLAUDE.md, README, docs/scanner-internals.md
- gap-matrix row marked DONE; future Items 2/3 retargeted to new filename

Failing-test-first (Iron Law): +2 knowledge staleness guards (era-anchor + no-refreeze) +1 scanner assertion (no stale model anchor in finding text). Suite 853 -> 856 green; zero snapshot drift; self-audit A(97) PASS. CHANGELOG / v5 plan / ratified gap-plan keep historical opus-4.7-patterns refs (correct record of past state).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ter3E2JSi1Khgmuf2kady8

knowledge/cache-telemetry-recipe.md

@@ -109,6 +109,6 @@ when structural signal alone isn't enough.
 
 ## See also
 
-- `knowledge/opus-4.7-patterns.md` — structural patterns the TOK scanner detects (CA-TOK-001..005)
+- `knowledge/prompt-cache-patterns.md` — structural patterns the TOK scanner detects (CA-TOK-001..005)
 - `knowledge/configuration-best-practices.md` — CLAUDE.md cache-stability guidance
 - `/config-audit tokens --with-telemetry-recipe` — surfaces a pointer to this file in JSON output

knowledge/configuration-best-practices.md

@@ -6,7 +6,7 @@
 
 ## CLAUDE.md
 
-1. **Optimise for prompt-cache stability.** Place stable content in the first 30 lines (cache-friendly prefix); volatile content (timestamps, dynamic counts, rolling activity logs) goes below that threshold or moves to an `@import`-ed file outside the cache prefix. On Opus 4.7 the dominant cost lever is cache reuse, not file length.[^200lines]
+1. **Optimise for prompt-cache stability.** Place stable content in the first 30 lines (cache-friendly prefix); volatile content (timestamps, dynamic counts, rolling activity logs) goes below that threshold or moves to an `@import`-ed file outside the cache prefix. On Opus 4.8 the dominant cost lever is cache reuse, not file length.[^200lines]
 2. **Use `@import` for specs/docs.** `@path/to/spec.md` inlines the file at session start. Max 5 hops, but keep chains ≤ 2 hops — every `@import` boundary fragments the prompt-cache prefix. Keeps the main file scannable.
 3. **Use HTML comments for maintainer notes.** `<!-- Updated 2026-01-01: reason -->` is stripped before context injection — zero token cost.
 4. **Put personal dev notes in `CLAUDE.local.md`**, not `CLAUDE.md`. Add `CLAUDE.local.md` to `.gitignore`. Team members' sandbox URLs should never appear in git.
@@ -94,4 +94,4 @@
 
 ---
 
-[^200lines]: The "keep CLAUDE.md under 200 lines" threshold was a Sonnet-era adherence heuristic — Sonnet's attention quality dropped on longer files, so trimming raw line count was the optimisation lever. Opus 4.7 uses prompt-cache structure as the dominant cost driver: the first 30 lines must stay byte-stable across turns to keep the cache hit, and `@import` boundaries fragment the cached prefix. A 400-line CLAUDE.md with stable structure outperforms a 150-line file whose top contains a daily-rolling activity log. See `knowledge/opus-4.7-patterns.md` for detection IDs (CA-TOK-001..003).
+[^200lines]: The "keep CLAUDE.md under 200 lines" threshold was a Sonnet-era adherence heuristic — Sonnet's attention quality dropped on longer files, so trimming raw line count was the optimisation lever. Opus 4.8 uses prompt-cache structure as the dominant cost driver: the first 30 lines must stay byte-stable across turns to keep the cache hit, and `@import` boundaries fragment the cached prefix. A 400-line CLAUDE.md with stable structure outperforms a 150-line file whose top contains a daily-rolling activity log. See `knowledge/prompt-cache-patterns.md` for detection IDs (CA-TOK-001..003).

knowledge/prompt-cache-patterns.md

@@ -1,14 +1,16 @@
-# Opus 4.7 Configuration Patterns
+# Prompt-Cache Configuration Patterns
 
-> Token-efficiency patterns for Claude Opus 4.7. Detection IDs map to TOK scanner findings.
-> Sources: research/01-opus-47-features-token-efficiency.md (Topic 1), research/04-prompt-caching-patterns.md (Topic 4). Last verified 2026-04-19.
+> Token-efficiency patterns for current Claude Code (defaults to Opus 4.8; Fable 5 is the top-capability model). Detection IDs map to TOK scanner findings.
+> Sources: research/01-opus-47-features-token-efficiency.md (Topic 1), research/04-prompt-caching-patterns.md (Topic 4). Patterns verified 2026-04-19; model-era anchor refreshed 2026-06-18.
 
-Opus 4.7 raises the cost ceiling per turn while expanding the context window
-and prompt-cache window. Net effect: cache reuse and tool-schema discipline
-become the dominant levers for keeping a session affordable. The patterns
-below are structural — they can be detected statically by reading config files
-without running a session. Cache hit-rate measurement requires runtime
-telemetry and is explicitly out of scope.
+Current Claude Code defaults to Opus 4.8 (Fable 5 is the top-capability model).
+On these models the cost ceiling per turn is high and both the context window
+and prompt-cache window are large, so cache reuse and tool-schema discipline
+are the dominant levers for keeping a session affordable. These patterns are
+properties of prompt-caching itself, not of any single model — they are
+structural and detectable statically by reading config files without running a
+session. Cache hit-rate measurement requires runtime telemetry and is
+explicitly out of scope.
 
 | # | Pattern | Detection (ID) | Severity | Fix |
 |---|---------|----------------|----------|-----|