docs(linkedin-studio): SB-S3b brief + plan — supersede arm (light-Voyage hardened)

Second sub-slice of SB-S3 (after S3a's reader landed). Adds an operator-gated,
explicitly-signalled supersede op to the consolidation engine: a temporal-update
candidate retires a stale fact (status: superseded, re-minted to an archival id,
replaced in place, retained as audit) and installs the new winner under the
canonical key-id. Bounded to scripts/brain/ — pure, deterministic, fully
unit-testable.

Operator-confirmed scope: temporal-update→supersede ONLY · winner→dynamic
(re-earn) · minimal `supersedes?: string` · retain superseded as audit.

Light-Voyage-hardened:
- brief-reviewer APPROVE-WITH-FIXES — 8 FIX folded (the load-bearing one: id
  lifecycle → winner-takes-key-id, retired fact re-minted, so mintEntityId(key)
  always points at the live fact).
- plan-critic REVISE → 2 BLOCK + 6 FIX folded: applyDiff must REPLACE-IN-PLACE
  (not copy → would dup the canonical key-id); proposeDiff must value-guard the
  supersede fork (a re-sent stale signal would self-supersede every run); plus
  --gather active-only filter + decay excludes superseded (else retired facts
  leak back as live context / spam stale flags).
- scope-guardian ALIGNED (0 creep / 0 gap).

Also reconciles brief-sb-s3a.md's stale DRAFT status (S3a landed 4fa411f).
No code yet — awaiting go-before-code.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RigJBiRFNtFZKCz21qNbQ4

docs/second-brain/brief-sb-s3a.md

@@ -1,7 +1,7 @@
 # Brief — SB-S3a: the first profile.md READER
 
 > **Slice:** SB-S3a (first sub-slice of SB-S3, the cross-silo + ops-centre arc step).
-> **Status:** DRAFT — awaiting operator "go" before any code. Light-Voyage hardening (brief-review → plan-critic → scope-guardian) pending.
+> **Status:** LANDED `4fa411f` (2026-06-23) — gate 95/0/0, `ASSERT_BASELINE_FLOOR` 80. Light-Voyage-hardened (brief-review APPROVE · scope-guardian ALIGNED · plan-critic REVISE→folded). SC1/2/3/6 gate-proven; SC4 inspection-pass; SC5 (read-back) deferred to a reloaded session.
 > **Predecessors:** SB-S0 (id/profile substrate) · SB-S1 (published-gold ingest) · SB-S2 (consolidation motor — *motor-only, no reader*).
 
 ## 1. Operator decision (2026-06-23)