feat(preamble): T3 — jargon dedup + terse-build flag (Phase A.2 + A.3)

A.2 jargon dedup: generate-writing-style.ts replaces the inlined 80-term
jargon list with a one-line pointer to scripts/jargon-list.json. The list
was duplicated into every tier-2+ skill (48 of 51 skills); inlining cost
was ~1.5 KB × 48 = ~70 KB across the corpus. Pointer cost is ~30 bytes per
skill. Agents Read the JSON once per session on first jargon term
encountered; thereafter the terms array is the canonical reference.

A.3 terse build flag: --explain-level=terse compresses preamble prose at
gen time. When the flag is set, writing-style collapses to a one-line
terse directive and completeness-section + confusion-protocol +
context-health are dropped entirely. The default build keeps the
runtime-conditional behavior intact (sections still render; the model
skips them when EXPLAIN_LEVEL: terse appears in the preamble echo). Terse
build is opt-in for users who want shipped skills to match their runtime
preference and avoid the per-session terse-mode dead prose.

TemplateContext gains an optional `explainLevel: 'default' | 'terse'`
field. Default builds set it to 'default'; --explain-level=terse sets
'terse'. Resolvers gate their output via `ctx?.explainLevel === 'terse'`.

Measured impact (default build, post-T3):
- Total corpus: 2,847 KB → 2,812 KB (saved 35 KB)
- ship.md: 160 → 159 KB
- plan-ceo-review.md: 128 → 127 KB
- Top 10 heaviest: all slightly smaller from jargon pointer

Larger compression lands in T4 (catalog trim) and T7 (atomic regen across
the full Phase A pipeline). The terse build path further compresses to
~711K tokens vs default ~725K (saved ~14K tokens corpus-wide).

Test plan:
- bun test test/gen-skill-docs.test.ts: 389 pass (no regression)
- bun test test/resolver-entry.test.ts: 6 pass
- bun test test/helpers/capture-parity-baseline.test.ts: 4 pass
- bun run gen:skill-docs --explain-level=terse: ship.md drops completeness +
  confusion-protocol + context-health sections; writing-style collapses to
  one-line terse directive

48 SKILL.md files updated (every tier-2+ skill picks up the jargon pointer).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

open-gstack-browser/SKILL.md

@@ -547,84 +547,7 @@ Applies to AskUserQuestion, user replies, and findings. AskUserQuestion Format i
 - User-turn override wins: if the current message asks for terse / no explanations / just the answer, skip this section.
 - Terse mode (EXPLAIN_LEVEL: terse): no glosses, no outcome-framing layer, shorter responses.
 
-Jargon list, gloss on first use if the term appears:
-- idempotent
-- idempotency
-- race condition
-- deadlock
-- cyclomatic complexity
-- N+1
-- N+1 query
-- backpressure
-- memoization
-- eventual consistency
-- CAP theorem
-- CORS
-- CSRF
-- XSS
-- SQL injection
-- prompt injection
-- DDoS
-- rate limit
-- throttle
-- circuit breaker
-- load balancer
-- reverse proxy
-- SSR
-- CSR
-- hydration
-- tree-shaking
-- bundle splitting
-- code splitting
-- hot reload
-- tombstone
-- soft delete
-- cascade delete
-- foreign key
-- composite index
-- covering index
-- OLTP
-- OLAP
-- sharding
-- replication lag
-- quorum
-- two-phase commit
-- saga
-- outbox pattern
-- inbox pattern
-- optimistic locking
-- pessimistic locking
-- thundering herd
-- cache stampede
-- bloom filter
-- consistent hashing
-- virtual DOM
-- reconciliation
-- closure
-- hoisting
-- tail call
-- GIL
-- zero-copy
-- mmap
-- cold start
-- warm start
-- green-blue deploy
-- canary deploy
-- feature flag
-- kill switch
-- dead letter queue
-- fan-out
-- fan-in
-- debounce
-- throttle (UI)
-- hydration mismatch
-- memory leak
-- GC pause
-- heap fragmentation
-- stack overflow
-- null pointer
-- dangling pointer
-- buffer overflow
+Curated jargon list lives at `~/.claude/skills/gstack/scripts/jargon-list.json` (80+ terms). On the first jargon term you encounter this session, Read that file once; treat the `terms` array as the canonical list. The list is repo-owned and may grow between releases.
 
 
 ## Completeness Principle — Boil the Lake