docs: fix capitalization losses + one text corruption from the contractions pass

Review pass on top of the previous commit (85a94671) turned up three
real issues its own vale-only verification didn't catch:

- 'has not' -> 'hasn't' fired inside 'has nothing', corrupting
  docs/swarm/README.md into 'hasn'thing to say upward'. Restored
  'has nothing'.
- ~44 hits where the original text was genuinely sentence-initial
  ('It is', 'That is', 'They are', 'What is', 'Do not', ...) got
  contracted in lowercase, silently de-capitalizing the start of a
  sentence. Checked each one's real surrounding text and capitalized
  the ones that needed it.
- Confirmed (by reading the actual text, not just trusting vale) that
  the 3 remaining 'is not'/'has not'/'it is' hits after those fixes are
  vale's own false positives: it matches these as a bare substring with
  no trailing word boundary, so it also fires on 'is nothing', 'has
  nothing', and the already-correct 'it isn't'. Left those alone --
  there's no real issue in the text.

Re-verified with a fresh vale run: the remaining 17 hits are exactly
the union of the 14 legitimate ALL-CAPS/bold-emphasis skips from the
first commit and these 3 false positives. Full accounting in
/agents/iris/state/haiku-batches/contractions-report.md.

docs/swarm/README.md

@@ -120,7 +120,7 @@ services.hyperhive.swarm.hives = {
 ```
 
 One attrset describing **every** hive in the swarm, **including this
-one**, keyed by that hive's `hiveName`. it's meant to be _identical on
+one**, keyed by that hive's `hiveName`. It's meant to be _identical on
 every host_ — write it once, share it, and each host reads it correctly
 because `services.hyperhive.hiveName` says which entry is itself.
 
@@ -138,7 +138,7 @@ evaluates cleanly points at a real machine that isn't the one you meant.
 > inside a swarm comes from the swarm root ([`ca.md`](ca.md)): every
 > hive chains to it, so one anchor replaces per-hive pinning entirely.
 > What that genuinely drops is trusting a hive whose root this swarm
-> does _not_ own — another swarm's, or one keeping its own CA. that's
+> does _not_ own — another swarm's, or one keeping its own CA. That's
 > a cross-swarm problem and wants a mechanism designed for it. (An
 > earlier `certFingerprint` field existed for exactly that gap, pinning
 > a peer's TLS leaf for hive-c0re's own peer HTTPS checks — removed
@@ -183,7 +183,7 @@ hiveName = "pr1ma";               hiveName = "edge";
 swarm.hives = { … };              swarm.hives = { … };   # byte-identical
 ```
 
-that's the point of the shape, and it removes a class of bug rather
+That's the point of the shape, and it removes a class of bug rather
 than saving typing: a per-host peer list let two hosts hold _different_
 facts about the same third hive — a stale endpoint, a rotated
 fingerprint — with nothing to detect the disagreement. One entry per
@@ -276,7 +276,7 @@ service it points at: `services.hyperhive.swarm.snapshotStore.{address,
 port}` tells this hive where the swarm's `btrfs receive` endpoint is, so
 `hivectl agent <name> subvol snapshot push` has somewhere to stream to.
 
-it's genuinely swarm-scoped rather than per-peer — a swarm has exactly
+It's genuinely swarm-scoped rather than per-peer — a swarm has exactly
 one store, because the receiver keys destinations by _agent_ so a
 migrating agent keeps one unbroken incremental chain. See
 [snapshot-store.md](../networking/snapshot-store.md).
@@ -303,7 +303,7 @@ still knows its own state — you just can't see it from here.
 
 A hive publishes only once it has been given the three
 `swarm.statusPublish` coordinates below. A hive that has not reads
-`never_reported` — it's not broken, it just hasn'thing to say upward.
+`never_reported` — it's not broken, it just has nothing to say upward.
 
 | freshness        | what to do about it                                                                                                                      |
 | ---------------- | ---------------------------------------------------------------------------------------------------------------------------------------- |