Tighten blog comments that are inaccurate, rot-prone, or exceed AGENTS.md "one short line max" #68

AGENTS.md states comments should default to "one short line max." Several comments added in #61 deviate — some are also factually wrong or contain references that will rot.

Inaccurate

• `components/site/Chrome.tsx:8-12` — claims a bare `#section` from `/blog/foo/` would resolve to `/blog/#section`. It actually resolves to `/blog/foo/#section` (fragment-only hrefs resolve against the current URL, not the parent path). The leading-slash point is correct; just fix the example.
• `lib/blog.ts:16-19` (`Slug` brand) — claims two constructor sites, `parseSlug` and `parseEntry`. Only `parseSlug` holds the `as Slug` cast; `parseEntry` is a strict consumer that throws on null. Rephrase: "The only constructor site is `parseSlug`; `parseEntry` consumes it and throws on null."

Rot risk / over-long

• `app/blog/page.tsx:14-21` — 8-line metadata block uses "previously left every blog route sharing a blank card." "Previously" relative to what? Tighten to 1–2 lines and drop the framing. Suggested: "`openGraph` shallow-replaces in Next 16, so re-pass `images` from `parent` or the root og image is dropped. Twitter `images` is set explicitly because the og→twitter fallback only fires at final resolution, not through `ResolvingMetadata`."
• `lib/blog.ts:7-11` (`SLUG_RE`) — 5 lines; drops the `js/stored-xss` CodeQL rule ID which will rot when the rule is renamed or the scanner changes. Keep the invariant claim; drop the rule reference.
• `lib/blog.ts:107-112` (memoise / "2N+3") — count is correct (verified: 3 `listPosts` callsites + 2 `getPost` callsites). 6 lines; trim the parentheticals enumerating callsites.
• `lib/blog.ts:125-131` (sort tie-break) — 7 lines; drop the HFS+ aside (irrelevant on modern macOS = APFS).

Found during PR review of #61.