Resolves the release recipe's carriers at read time

[johnnyt]

What

.claude/wurk/release.md's "Where the fields live" section named the README
install pin by a literal version and a literal README line number. Both had
rotted: the version was several majors behind the published one, and the line
had moved down as the README grew. The version file's line number was still
correct today but rots by exactly the same mechanism, so it goes with it.

Both carriers are now described by shape and resolved with a grep the reader
runs at read time:

grep -n '@version "' mix.exs
grep -n 'predicator, "~>' README.md

Each resolves to exactly one line on main today. A paragraph in "The README
pin's exact form" records why this file carries no version string and no line
number anywhere, and what to do if the two carriers ever disagree on major or
minor.

This is the same rotting-reference class the sibling recipes fixed in sb-0id2
(statifier_blocks) and sui-040 (statifier-ui), and their files are the
precedent this one follows.

What this does not touch

mix.exs, README.md, CHANGELOG.md, changelog.d/ and the manifest are all
unchanged. The recipe document is the only file in the diff. No changelog
fragment: changelog.d/README.md excludes agent-tooling and documentation
changes.

Provenance

Beyond the README pin the bead names, the same edit removes the mix.exs:5
line reference in the adjacent bullet. The bead's second acceptance criterion
asks for every other version-specific claim in the file to be checked, and a
file that resolves one carrier by grep while pinning the other by line number
would have re-grown the defect at the next insert. Reported here rather than
made silently.

Verification

Docs-only under CLAUDE.md's authority table (a change touching no Elixir code
has no gate to run and commits on review of the diff); CI runs the gate on the
branch. Acceptance criteria machine-checked against the committed file:

• no version-like string (grep -nE '[0-9]+\.[0-9]+') and no file:line
  reference (grep -nE '\.(exs|ex|md|json):[0-9]+') remain in the file - both
  greps return nothing; the only digits left are the two cited bead ids and an
  ADR number;
• both resolver greps return exactly one line each on this branch;
• every other claim in the file re-verified against the tree: the manifest's
  release.readme_pin is true, the pin drops its patch component,
  CHANGELOG.md carries no ## [Unreleased] heading, changelog.d/ holds only
  its README.md, and docs/adr/0006-* exists.

Refs: px-jci

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