ci(pdf): quote GITHUB_ENV and GITHUB_OUTPUT redirects flagged by actionlint SC2086

[willgriffin]

Quotes the seven unquoted $GITHUB_ENV / $GITHUB_OUTPUT redirect targets that
actionlint flags as SC2086 across three workflows.

This is the same pattern already applied to changeset-check.yml in #122, which
was scoped to #121 and deliberately left the rest alone.

Changes

File	Statement
on-pull-request.yml	STORE_PATH=… → >> "$GITHUB_ENV"
on-pull-request.yml	bump=$bump → >> "$GITHUB_OUTPUT"
publish.yml	STORE_PATH=… → >> "$GITHUB_ENV"
publish.yml	changed=false → >> "$GITHUB_OUTPUT"
publish.yml	changed=true → >> "$GITHUB_OUTPUT"
publish.yml	version=… → >> "$GITHUB_OUTPUT"
test.yml	STORE_PATH=… → >> "$GITHUB_ENV"

Scope

Lint hygiene only; no behavioural change. None of these scripts consume untrusted
input — actionlint reports no is potentially untrusted findings in these three
files. The security-relevant untrusted-input finding lives in changeset-check.yml
and is tracked by #121 / #122.

Verification

actionlint before and after, from this branch:

• Before: 9 findings — 7 SC2086 in these three files, plus 2 in changeset-check.yml.
• After: 2 findings, both in changeset-check.yml (SC2086 + untrusted PR title),
  which ci: pass untrusted pull-request fields through env in changeset-check #122 fixes. Zero findings remain in the three files this PR touches.

pnpm typecheck, pnpm lint, pnpm test (162 passed / 17 files) and pnpm build
are all green. pnpm docs:api was not run — no public API or JSDoc surface changed.

Release intent

Labelled skip-changeset: the diff touches only .github/workflows/**, no
release-sensitive path, and the commit subject is non-releaseable.

Closes #125

{
  "schema": "hv-agent-run:v1",
  "runtime": "claude",
  "session": "dca0aa48-4946-43ba-940b-51143a9e4a8b",
  "issue": "https://github.com/happyvertical/pdf/issues/125",
  "policy_revision": "1.0.0",
  "validation": [
    "actionlint",
    "pnpm typecheck",
    "pnpm lint",
    "pnpm test",
    "pnpm build"
  ]
}

[github-actions]

Release Preview

This PR title will not trigger an automatic release on squash merge.

Use a releaseable conventional PR title like fix(pdf): ..., feat(pdf): ..., or chore(deps): ... if this change should publish automatically.

Otherwise, add a manual changeset or apply the skip-changeset label if no release is needed.