fix(#3576): repair all 43 dead references/ cites and gate the canonical resolvable form (#3596)

* test(#3576): gate shipped reference citations on the canonical resolvable form

Failing-first gate for #3576: a backticked bare references/<name>.md cite
resolves from no install location (agents, workflows, and references all
install where a bare relative references/ path is dead). The gate walks the
runtime-loaded trees the issue prescribes, strips @~/ include tokens
PER-TOKEN (a line-skip guard would miss a bare cite sharing a line with an
include — the issue-named trap), pins the genuinely relative ../ href and
canonical forms as non-offenders, and checks canonical cite targets exist.
43 offenders today across 19 files.

* fix(#3576): repair all 43 dead references/ cites to the canonical resolvable form

Every backticked bare references/<name>.md cite across the 19 shipped files
rewritten to gsd-core/references/<name>.md — the form every required_reading
block and @~/ include already uses, and the only form that resolves from any
install location. All 20 cited targets verified to exist; the one genuinely
relative href (plan-phase.md's ../references/mvp-concepts.md) is untouched
(the repair is backtick-anchored). Growth acks: new fragment for the three
first-time paths, #3206-pattern appends to the five fragments already naming
the other grown files (two ack sources may never name the same path).
execute-phase.md lands at 93,391/93,400 and gsd-executor.md at 49,150/49,152
— exactly the issue's projections; every repair fits.

* fix(#3576): drop stale default.md growth ack (nested modes file is hash-attributed, not growth-ratcheted)

Review finding: the emitted-attribution ratchet covers only top-level
workflows/ + agents/ files; discuss-phase/modes/default.md's delta is
source-attributed, so acknowledging its growth is a stale entry the
differential lane fails on.

* chore(#3576): add changeset fragment

* chore(#3576): backfill changeset pr number

---------

Co-authored-by: sim <sim@local>

gsd-core/references/revision-loop.md

@@ -70,7 +70,7 @@ issues. You must reduce the count or the loop will terminate.
 If issues persist after 3 revision cycles:
 
 1. Present remaining issues to the user
-2. Use gate prompt (pattern: yes-no from `references/gate-prompts.md`):
+2. Use gate prompt (pattern: yes-no from `gsd-core/references/gate-prompts.md`):
    question: "Issues remain after 3 revision attempts. Proceed with current output?"
    header: "Proceed?"
    options: