docs: trim AI writing tells from READMEs and docs prose

Drop magic adverbs (silently, arguably), a stakes-inflation flourish,
and the bold-first Snippets bullets; de-duplicate the "usable artifact,
not a checkpoint" line shared by the README and roadmap.

docs/postmortems/2026-07-05-spike3-sd-cmd59.md

@@ -51,7 +51,7 @@ runs **SD-only** (see "EPD bus lock" below).
    against marginal signal integrity.
 3. Verified the card on the Mac: `Windows_FAT_32 TYPOENA`, 33.6 GB partition on
    a 133 GB card, **healthy and readable**. Rules out a dead card / wrong FS.
-4. Read the esp-idf SD init source: the CMD8 handler *silently tolerates* the
+4. Read the esp-idf SD init source: the CMD8 handler *tolerates* the
    same `ESP_ERR_NOT_SUPPORTED` (treats it as "not a v2 card"), while CMD59's
    does not. So the failure might be a persistent bad response, not a CMD59
    one-off — needed the raw R1 bytes to tell.

docs/postmortems/2026-07-05-spike7-gix-https-push.md

@@ -80,7 +80,7 @@ Implementation notes that carry into the real module:
 
 ## What it does *not* prove — the next gate
 
-The risk moved **with** the kill-switch, and arguably got harder. ADR-004 chose
+The risk moved **with** the kill-switch and got harder. ADR-004 chose
 gix *specifically to avoid* libgit2's C cross-compile to xtensa; falling back to
 libgit2 re-introduces exactly that. The open question is now: