fix(#4730): decode entity-escaped ampersands before verify-command-paths segment splitting (#4755)

* fix(#4730): decode entity-escaped ampersands before verify-command-paths segment splitting

Planners emit <automated> bodies with the chain operator entity-escaped
(`&amp;&amp;`), and the executing agent reads the decoded (rendered) form.
The grounding probe split the raw text on &&/||/;/newline without decoding
first, so `&amp;&amp;` was cut at its semicolons and a cd-form target
absorbed the trailing `&amp` fragment — an existing directory was reported
missing_dir (blocker), feeding false blockers into the revision loop.

Decode `&amp;` → `&` inside resolveVerifyCommandTarget, after
result.command captures the text verbatim and before any segment splitting
or target resolution, so the escaped and literal forms of the same command
produce identical verdicts. Module-private helper beside splitSegments,
mirroring the sibling src/verify.cts decodeEntityAmps (#3611); the two
gates are separate modules and neither imports the other.

Regression coverage pins escaped/literal verdict parity for: existing dir
+ manifest (ok), missing dir (missing_dir blocker kept), dir without
manifest (no_manifest blocker kept), --prefix form, a literal & inside a
quoted dir name, and a full probePhaseVerifyCommands pass whose reported
command field stays verbatim.

* docs(#4730): use the documented pr:0 placeholder in the changeset fragment

The fragment carried pr: 4730 — the ISSUE number, the exact guess-shape
DEFECT.CHANGESET-PR-FIELD-DRIFT (#3316, #3325) exists to catch: it parses
as a positive integer so local lint passed, but on a real PR run the
drift check would fail it against the actual PR number. CONTRIBUTING.md
documents pr: 0 as the deliberate unresolved placeholder used during
initial commit before the PR number exists (scripts/changeset/new.cjs
accepts 0 for exactly this reason); the gate's fail_invalid_fragment on
an unbackfilled 0 is the designed backfill enforcement, not a defect.

No production or test changes. Backfill pr: with the real PR number
once the PR is created.

* docs(#4730): backfill changeset pr field with the real PR number

pr: 0 → pr: 4755 (the PR carrying this fix), completing the
documented placeholder workflow; the changeset gate's content
validation can now pass.

---------

Co-authored-by: TwistedRiCen <16397953+TwistedRiCen@users.noreply.github.com>
Co-authored-by: Tom Boucher <trekkie@nomorestars.com>

src/verify-command-grounding.cts

@@ -530,6 +530,26 @@ function splitSegments(cmd: string): string[] {
     .filter(s => s.length > 0);
 }
 
+/**
+ * Decode entity-escaped ampersands (`&` → `&`) — #4730, the grounding
+ * gate's share of the #3611 defect. Planners emit `<automated>` bodies with
+ * `&amp;&amp;` as the chain operator, and the executing agent reads the
+ * decoded (rendered) form. Without this decode, `splitSegments` cuts
+ * `&amp;&amp;` at its semicolons and a `cd` target absorbs the trailing
+ * `&amp` fragment (`rawTarget: "src &amp"`), reporting an existing directory
+ * as a `missing_dir` blocker. Applied to the command text inside
+ * `resolveVerifyCommandTarget` — before any segment splitting or target
+ * resolution, after `result.command` has captured the text verbatim — so the
+ * escaped and literal forms of the same command produce identical verdicts.
+ * Kept module-private beside `splitSegments`, mirroring the sibling
+ * `src/verify.cts`'s own private `decodeEntityAmps` (#3611): the two gates
+ * are separate modules that independently parse `<automated>` text, and
+ * neither imports the other.
+ */
+function decodeEntityAmps(s: string): string {
+  return s.replace(/&amp;/g, '&');
+}
+
 /** Strip a single matching pair of surrounding quotes, if present. */
 function stripQuotes(s: string): string {
   if (s.length >= 2) {
@@ -655,7 +675,10 @@ function resolveVerifyCommandTarget(command: unknown, options?: ResolveOptions):
   if (typeof command !== 'string') return result;
   result.command = command;
 
-  const trimmed = command.trim();
+  // #4730: decode entity-escaped ampersands BEFORE segment splitting (see
+  // decodeEntityAmps) so the chain operator is visible to the splitter and
+  // the verdict matches what the executing agent's decoded form grounds to.
+  const trimmed = decodeEntityAmps(command.trim());
   if (trimmed === '') return result;
 
   // Nyquist "MISSING — Wave 0 must create …" sentinel; Dimension 8 owns it.