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/workflows/execute-phase.md

@@ -709,7 +709,7 @@ increases monotonically across waves. `{status}` is `complete` (success),
 
        <worktree_branch_check>
        ORCHESTRATOR build-time embed (NOT a sub-agent runtime step): before this dispatch, read `gsd-core/references/worktree-branch-check.md`, substitute `{EXPECTED_BASE}` with the base SHA captured above ({EXPECTED_BASE}), and replace this note with that fragment's `<worktree_branch_check>` block so the dispatched prompt carries the runnable guard verbatim — do not pass this instruction through in its place.
-       Per-commit HEAD/cwd-drift/path-guard: `agents/gsd-executor.md` steps 0/0a/0b + `references/worktree-path-safety.md` (in <execution_context>).
+       Per-commit HEAD/cwd-drift/path-guard: `agents/gsd-executor.md` steps 0/0a/0b + `gsd-core/references/worktree-path-safety.md` (in <execution_context>).
        </worktree_branch_check>
 
        <parallel_execution>