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/agent-lifecycle/persistence.md

@@ -72,7 +72,7 @@ power-intent registry:
   last_fired_at_unix / last_result`. `ON DELETE CASCADE` from
   `scheduled_prompts(id)` — requires `PRAGMA foreign_keys = ON`
   per connection (set at open).
-- `agent_power` — one tiny row per agent: `agent PK / wanted (up |
+- `agent_power` — one row per agent: `agent PK / wanted (up |
   offline) / updated_at`, owned by `hive-c0re/src/stores/power.rs`.
   This is the durable power *intent* the job queue reconciles the
   observed container state against; intent survives hive-c0re
@@ -158,7 +158,7 @@ host-side). Best-effort and created on first write
 (`CREATE TABLE IF NOT EXISTS`), so it's absent until a bash
 task runs.
 
-turn-stats.sqlite has **no vacuum** — it's one tiny row per turn
+turn-stats.sqlite has **no vacuum** — it's one small row per turn
 (~hundreds of KB even over months), read directly by the `/stats` page
 and the hive-wide stats view, so pruning it would only lose trend
 history for no space gain.
@@ -409,7 +409,7 @@ Contents:
 
 The root agent has the meta dir RO-mounted at `/meta/`.
 
-There is no longer a `.meta-migration-done` marker: the
+The `.meta-migration-done` marker no longer exists: the
 one-shot container repoint it guarded has been removed, since
 containers are rendered onto `meta#<n>` at creation. A stale
 marker file left over from an older hive is inert and can be
@@ -516,7 +516,7 @@ marker-guarded so the substantive moves only happen once per
 container lifetime:
 
 1. **`${homeDir}` exists with the right ownership** — covers the
-   very first boot before `useradd`'s `createHome` has had a
+   the first boot before `useradd`'s `createHome` has had a
    chance to chown. Also re-applies on every rebuild in case the
    meta-flake's per-agent name evolves (rare).
 2. **Migrate any leftover `/root/.claude` content into