Publish the first publication-lifecycle measurement report edition (≥20 records)

## Problem

`specs/022-publication-lifecycle-measurement` and its tooling landed in #364
(decision-log entry 83, closing #354), but no report edition can be written
yet: per FR-017 the first edition of `docs/publication-lifecycle-report.md` is
published only once **≥ 20** opt-in measurement records exist under
`metrics/publication-lifecycle/`. Those records only accrue as real capability
publications happen and their authors choose to contribute a record.

## Definition of done

- [ ] At least 20 `metrics/publication-lifecycle/pr-.json` records are merged.
- [ ] `docs/publication-lifecycle-report.md` is rewritten in place as the first
real edition, following the methodology section fixed in that file:
per-bucket (`simple` / `complex`) `n`, median + p90 `hours_open_to_conclusion`,
median `review_rounds`, and `ci_failure_counts` category frequencies.
- [ ] The edition states `n`, gives min–max ranges for any bucket with `n < 30`,
and declines the simple-vs-complex comparison if either bucket has `n < 10`.
- [ ] The edition documents sample size, self-selected-opt-in selection bias,
retention, and uncertainty (already templated).
- [ ] `docs/decision-log.md` gets a short entry recording the first edition and
any threshold tuning.

## Notes

- No spec change required — this is FR-016/FR-017 execution under the
already-approved spec 022.
- Nothing automated consumes the report (FR-018); it is advisory prose only.
- If adoption is slow, this issue simply waits. Do not lower the threshold to
publish sooner without recording that decision.

Wait for at least 20 merged metrics/publication-lifecycle/pr-.json records, then read the methodology section in docs/publication-lifecycle-report.md and calculate the specified per-bucket metrics and ranges. Rewrite that report with the templated bias, retention, and uncertainty notes, and add a short first-edition or threshold-tuning entry to docs/decision-log.md.

Written by the indexing model from the issue text.