[marcinobel]

The runbook documents both ways to approve the production gate, but never mentions the
PreToolUse hook that enforces them — so a denied approval reads as a broken release rather than
as the safety property working. That is exactly how it presented while releasing 0.1.5: two
approval attempts were refused and nothing in the docs explained why.

Adds a "The agent gate hook" subsection to §5 recording the non-obvious part: the hook reads
REVCLI_GATE_APPROVED from its own environment, inherited from the agent process, so the
variable is resolved before the shell exists. Setting it inline on the command, or exporting it
earlier in the same command, both still get denied. Only a variable present when the agent
launches lets the call through. The section keeps the existing steer that approving by hand in
the UI is the preferred path.

Docs-only. Verified locally on this branch: npm run typecheck exit 0, npm test 297 passed
(17 files) exit 0, npm run build exit 0, npm run check:pack exit 0. The repo has no markdown
linter, so nothing here validates the prose itself.

Reviewer note: this body deliberately does not quote the two command strings the new section
contains. The hook matches raw tool input, so a body quoting them is refused — which is part of
what the section documents.