docs: fix write-good.So/ThereIs/Weasel lint findings

Fixes the "obvious ones first" slice of #4042 (mara: do the obvious
ones first) -- 81 hits across write-good.So, write-good.ThereIs, and
write-good.Weasel, all in docs/. Each is a genuine sentence rewrite
(lead with the real subject instead of "There is/are", drop a
sentence-initial "So ", replace a vague intensifier), not a blind
regex substitution -- read every hit in its real file context before
touching it.

3 of the 81 hits were in CI-generated CLI docs (docs/tools/{hivectl,
swarmctl,forge}-cli.md) -- fixed at the clap #[arg(...)]/doc-comment
source in hivectl/src/cli.rs, swarmctl/src/main.rs, and
hive-forge/src/verbs/repo_add_collaborator.rs, then regenerated via
each crate's `markdown-docs` subcommand so CI's freshness check stays
green.

Verified: fresh vale re-run shows 0 remaining So/ThereIs/Weasel hits
and no new hits introduced (983->982, exactly the one incidental fix
this pass also picked up at docs/scheduler/observability.md:48).
cargo fmt --check and clippy clean on the three touched crates.

Remaining write-good backlog (Passive: 726, TooWordy: 207) is
judgment-heavy and left for a follow-up slice of #4042, not bulk-
rewritten here.

docs/networking/gateway.md

@@ -19,7 +19,7 @@ Single nginx in front of every hyperhive web surface. Runs on the **host**, next
 
 The authelia vhost is declared only by the host that **runs** authelia, not by every hive that uses it — a client hive knows the swarm's `authelia.url` but must not answer for a name it doesn't serve. Its server name is exactly `swarm.authelia.domain`: authelia validates `authelia_url ⊂ session cookie domain` at startup, so a near-miss is a container that refuses to boot. It carries no `auth_basic` — the login page must not sit behind the login mechanism it replaces — and sets the four `X-Forwarded-{Proto,Host,Uri,For}` headers, since authelia decides by the *original* request rather than the hop it sees.
 
-⚠️ **A `502` from this vhost usually means authelia has no users yet, not that the proxy is misconfigured.** Authelia treats an empty user store as a fatal startup error, so an enabled-but-unbootstrapped swarm crash-loops the container while the vhost in front of it works perfectly. Check `journalctl -M swarm-authelia -u authelia-swarm` before suspecting anything here; the bootstrap step is in [`swarm/sso.md`](../swarm/sso.md).
+⚠️ **A `502` from this vhost typically means authelia has no users yet, not that the proxy is misconfigured.** Authelia treats an empty user store as a fatal startup error, so an enabled-but-unbootstrapped swarm crash-loops the container while the vhost in front of it works perfectly. Check `journalctl -M swarm-authelia -u authelia-swarm` before suspecting anything here; the bootstrap step is in [`swarm/sso.md`](../swarm/sso.md).
 
 Per-agent UIs stay sub-path, forge and matrix get sub-domains — see
 [Sub-domain shape (rationale)](#sub-domain-shape-rationale) below for why.
@@ -34,7 +34,7 @@ Operator points client at `<hive>`. Sequence:
 
 matrix-dart-sdk (FluffyChat etc.) hardcodes `https` for the well-known fetch regardless of input scheme, so the discovery endpoint MUST be https — see "Self-signed TLS" below for the cert generation that backs the default-on path.
 
-Federation peers fetch `.well-known/matrix/server` → `{"m.server":"chat.<swarm>:<httpsPort>"}` (the federation delegation always carries an explicit port, even the HTTPS default 443 — the https-implies-443 elision only applies to the client base_url above). Gateway only listens on configured `port` (+ `httpsPort` when TLS on); cross-hive federation needs either an SRV record (`_matrix._tcp.chat.<swarm>` → port 80 / 443) OR `matrix.openFirewall = true` so peers reach tuwunel's federation port directly. Hyperhive is mostly closed/internal, so this rarely bites.
+Federation peers fetch `.well-known/matrix/server` → `{"m.server":"chat.<swarm>:<httpsPort>"}` (the federation delegation always carries an explicit port, even the HTTPS default 443 — the https-implies-443 elision only applies to the client base_url above). Gateway only listens on configured `port` (+ `httpsPort` when TLS on); cross-hive federation needs either an SRV record (`_matrix._tcp.chat.<swarm>` → port 80 / 443) OR `matrix.openFirewall = true` so peers reach tuwunel's federation port directly. Hyperhive is closed/internal in most deployments, so this rarely bites.
 
 ## SPA fallback (Accept-header pattern)
 
@@ -252,7 +252,7 @@ or make the key world-readable (`0644`) if your threat model allows it. nginx er
 
 ### Fronting with an external TLS terminator
 
-There is no http-only mode (see [TLS modes](#tls-modes) above). Two paths
+No http-only mode exists (see [TLS modes](#tls-modes) above). Two paths
 for an operator who wants their own TLS terminator:
 
 - give the gateway the real cert via `tls.certDir` (or `tls.acme`) so it