docs: fix 329 Microsoft.Contractions hits with proper safety checks

Apply contraction fixes across ~40 doc files (setup, integrations, lifecycle,
networking, scheduler, swarm, tools, trust-boundary, UI, etc.). Skipped 14 hits:
- 10 where words appear in ALL CAPS for deliberate emphasis (is NOT, do NOT, etc.)
- 4 where text could not be safely located due to markdown formatting or column position

Applied via systematic scan with checks for fenced code blocks, inline code spans,
and intentional caps. Preserves sentence-initial capitalization throughout.

docs/integrations/github.md

@@ -28,7 +28,7 @@ into every agent, so no agent ships the `gh` wrapper or credential helper.
 (`hyperhive.github.enable` also exists per-agent for completeness, but the
 hive-wide host switch is the intended control.)
 
-github.com only. The token **value** never touches nix — it is written to
+github.com only. The token **value** never touches nix — it's written to
 `<state>/github-token` separately (see [Provisioning](#provisioning)).
 
 ## Provisioning
@@ -88,7 +88,7 @@ minimal environment that wouldn't carry one.
 ### Notifications
 
 `hive-github-notify` polls github.com for the agent, turning each unread
-notification thread into a todo. It is a **separate binary and a
+notification thread into a todo. it's a **separate binary and a
 separate systemd unit** from the internal forge's poller
 (`hive-forge-notify`, see [forge.md](forge.md#notification-poller-hive-forge-notifysrcnotifyrs)),
 installed by `nix/agent-modules/github.nix` under
@@ -99,12 +99,12 @@ path, not a new package.
 Two units rather than one daemon with two loops, because it puts the
 decision in nix: a hive built without this module has **no github poller
 in its closure at all**, which is what makes GitHub access separable
-rather than merely switched off. It is also why this is not a cargo
+rather than merely switched off. it's also why this isn't a cargo
 feature — a feature would unify across the workspace and cost every
 crate its build cache.
 
 At runtime the poller needs the PAT above. No PAT, no polling: the unit
-logs why and exits 0, which is why it is `Restart = on-failure` and
+logs why and exits 0, which is why it's `Restart = on-failure` and
 never `always` — a clean exit on a PAT-less agent must not become a
 restart loop.
 
@@ -114,7 +114,7 @@ parse serves both: `id`, `repository.full_name`,
 for field. The two real differences are absorbed by lenient
 deserializers — GitHub sends the thread id as a _string_ where Forgejo
 sends a number, and says `PullRequest` where Forgejo says `Pull`. Todo
-keys are prefixed `gh:<id>` so a github thread id cannot collide with a
+keys are prefixed `gh:<id>` so a github thread id can't collide with a
 forge one.
 
 Two host differences worth knowing before touching this code:
@@ -122,15 +122,15 @@ Two host differences worth knowing before touching this code:
 - **Auth scheme, not just value.** Forgejo takes
   `Authorization: token <t>`; GitHub wants `Bearer <t>` plus `Accept:
 application/vnd.github+json`, `X-GitHub-Api-Version` and a
-  `User-Agent`. Sending Forgejo's form to GitHub does not error — it
+  `User-Agent`. Sending Forgejo's form to GitHub doesn't error — it
   authenticates as _nobody_ and silently drops to the unauthenticated
   rate limit. The cheap way to tell the two apart is the rate-limit
   header: `x-ratelimit-remaining` near 5000 is an authenticated user,
   near 60 is anonymous.
 - **GitHub sets the cadence.** It returns `X-Poll-Interval` (60s in
   practice, slower than our own tick) and rate-limits callers who ignore
-  it, so the loop re-arms to the server's interval whenever that is
-  _slower_ than ours. A hint faster than our own tick is not a reason to
+  it, so the loop re-arms to the server's interval whenever that's
+  _slower_ than ours. A hint faster than our own tick isn't a reason to
   poll harder.
 
 ⚠️ **This needs the `notifications` scope on the PAT.** A token minted