Task: Describe loopwright by its principles, not its stack #13

Goal

Make loopwright describe itself by its principles first and its stack second, in
the four places where its identity is currently written through the stack. The
most consequential of the four is .loopwright/claude-md-section.md: it is the
block install.sh injects into every host repo's CLAUDE.md, so it is how
loopwright introduces itself to everyone who adopts it. Leaving it as is would
mean the source repo talks about principles while every adopter still reads a
description by directory and test runner.

What "nothing is removed" means here, precisely, because one line is an
exception: every requirement fact survives — Node ≥ 20.11, the need for a
package.json, npm/pnpm/yarn support. They stop being the identity, but they stay
stated. The one line whose truth value changes, not just its framing, is the
merge-authority sentence at README.md:142-143: "always the human's decision"
becomes the human's decision by default. That is P8, and it is a real change,
not a reframing.

The checkable test for "principles first", so this is not a matter of taste:
in each rewritten lead, the first sentence must name a concrete opinion — the
tone to match is docs/loopwright/quality-gate.md:3-5 — and must not contain
"JS/TS" or "vendor" before that opinion has been stated. Any coder and any
reviewer can run that test without judgement.

Acceptance criteria

• README.md:3-6 leads with a named opinion and the "vendor it into any
  JS/TS repo" clause follows rather than defines — per the textual test above.
• README.md:89 ("Your stack, not loopwright's") and README.md:173 (the
  parenthetical "loopwright targets JS/TS repos") no longer frame identity as
  the stack, while remaining factually accurate about what is required.
  README.md:174 (package managers) carries no identity framing and needs no
  edit.
• README.md:158-169 ("How it's wired") gains a row for
  docs/loopwright/principles.md.
• README.md:142-143 — "Two rules hold the whole thing together: the gate
  is the only source of truth for "done", and merging is always the
  human's decision." — is reconciled with P8: merge is the human's by
  default, automating it is an explicit opt-in. This is the second site of the
  absolute rule, and README.md has only this draft as its owner.
• CLAUDE.md and .loopwright/claude-md-section.md both point at three docs
  with principles first, and both describe loopwright by what it is
  opinionated about before naming .loopwright/. This includes
  CLAUDE.md:1-6, the preamble above the <!-- loopwright:start -->
  marker — it is unique to this repo, is not shared with
  claude-md-section.md, and is the single worst identity-by-mechanism site
  in the repo ("the engine lives in .loopwright/scripts/, its tests in
  .loopwright/tests/").
• package.json:4 describes loopwright by its process opinions rather than
  as a "quality layer for AI-assisted JS/TS repos".
• No factual requirement is lost in the rewrite: Node ≥ 20.11, the need for a
  package.json, and npm/pnpm/yarn support remain stated somewhere in
  README.md.

Pointers into the RFC

• Context → the exact sentences that currently carry the stack framing, with
  their locations.
• Scope, third bullet → the four files, why claude-md-section.md is the most
  important of them, and the README.md:142-143 reconciliation.
• "Why the contested branches settled where they did" → the P2/P8 split, which
  is what README.md:142-143 has to be rewritten against: the gate half of that
  sentence survives as P2, the merge half becomes P8's default.
• docs/loopwright/quality-gate.md:3-5 is the one place in the repo that already
  states purpose process-first; it is the tone to match.

Blocked by

#11 — these files link to the doc and summarise it, so it has
to exist first.