docs: workflow, Dockerfile and brand-tool comments say what each does (#6277)

release.yml, the Dockerfile and tools/gen-brand-assets.py keep every
constraint their comments explain (the tag map, the gate, immutable tags,
the shared-daemon Postgres guard, the version/channel split) and drop the
history around them: rule and family-idea numbers, issue and run ids,
dates, an operator quote, the "this used to say the opposite" paragraphs
and one-runner timings.

Corrected: the Dockerfile said client/ is filled on tag pushes only; every
build fills it (dev and tag push bundle their own APK, main bundles the
latest release's).

Only full-line `#` comments changed: non-comment lines are identical to
HEAD in all three files, and the three run: scripts whose text changed
differ only in shell comment lines. The release guard tests match raw
workflow text; none of their required or forbidden strings appear in the
new comments.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/gen-brand-assets.py

@@ -180,11 +180,10 @@ def main():
              "       Literal colours, for any consumer that cannot inline the SVG and\n"
              "       therefore cannot supply a currentColor. -->\n"))
 
-    # The tab icon is the full mark too (#5267). A hand-drawn reduced hat used
-    # to stand in at tab size because the art loses detail at 16px, but a
-    # redrawing reads as a different logo. The full mark keeps the logo's own
-    # shape, and a tab on a high-resolution screen draws it from 32px, where it
-    # holds. Do not swap a redrawn form back in here.
+    # The tab icon is the full mark too. A hand-drawn reduced form would lose
+    # less detail at 16px, but a redrawing reads as a different logo; the full
+    # mark keeps the logo's own shape, and a tab on a high-resolution screen
+    # draws it from 32px, where it holds. Do not swap a redrawn form in here.
     (ROOT / "web/static/brand/favicon.svg").write_text(svg_doc(
         vb, tr, "currentColor", ACCENT, hat_d, notes_d,
         head="  <!-- Generated by tools/gen-brand-assets.py — do not edit by hand.\n"