revert(pkgs): leave the duplicate chromium — honestly, and with the numbers

Bernardo on #121 (shipped in 0b464af): "Let's leave it honestly. Sounds too
much work for a negligible gain." Agreed, and his own reasoning is the
argument: the fix worked, but it substitutes into a buildCommand nixpkgs owns,
which couples us to wrapper internals and has a SILENT no-op failure mode —
so it also needed a permanent check, because nothing about a returning
duplicate breaks a build. That standing maintenance cost buys ~195 MiB of
download and ~19 MiB of disk. Boring beats clever at that exchange rate.

Removed the overlay and checks.chromium-single-closure. The template HM closure
is back to 9.38 GiB with the duplicate present — verified by closure, not by
reading the diff. overlays.default now carries a comment saying the duplicate
is known and deliberate, where the next person will look for it.

The ROADMAP entry stays, downgraded from ✓ to ✗ decided-against: it holds the
measurement, the approach that worked (self-contained -wv copy; repoint the
wrapper's share/* symlinks; .override composes with overrideAttrs), and the
commit to recover it from. The bug is real and worth an upstream patch — the
wrapper should take its desktop entry from the variant it wraps, which helps
every NixOS user with enableWideVine, not only us. Revisit locally if #120's
netinstall ships, since download is the one axis this moves.

What survives is worth more than the fix, and is stamped on #120: closure size
is not disk size and is not image size — measure the artifact. Removing a
687 MiB path moved the ISO by 8 KiB, because mksquashfs dedupes duplicate files
and auto-optimise-store hardlinks them. Without that caveat, #120's "drop the
pin, save 4 GiB" would have evaporated at the squashfs exactly as this did.

V0: nix flake check --no-build passes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

agent/JOURNAL.md

@@ -19,7 +19,32 @@ Template:
 
 ---
 
-## 2026-07-14 — #121: one chromium, not two — 687 MiB off every install (this commit)
+## 2026-07-14 — #121 reverted: the fix worked, the gain didn't survive measuring (this commit)
+- **Task:** Bernardo's call on #121 (shipped 0b464af, reverted here): *"Let's
+  leave it honestly. Sounds too much work for a negligible gain."*
+- **Did:** removed the chromium overlay + `checks.chromium-single-closure`;
+  template HM closure back to 9.38 GiB and the duplicate unwrapped chromium is
+  back, deliberately. `overlays.default` carries a comment saying so, and the
+  ROADMAP entry is now a **✗ decided-against** record holding the measurement,
+  the working approach, and the commit to recover it from.
+- **Why this was right:** the fix worked, but it substitutes into a
+  `buildCommand` nixpkgs owns — coupling us to wrapper internals with a
+  *silent no-op* failure mode, which is why it needed a permanent check too.
+  That standing cost buys ~195 MiB of download and ~19 MiB of disk. Boring
+  beats clever at that exchange rate (CONVENTIONS).
+- **The lesson that outlives it, and the real product of the last two items:**
+  **closure size is not disk size and is not image size — measure the
+  artifact.** Removing a 687 MiB path moved the ISO by 8 KiB, because
+  mksquashfs dedupes duplicate files and `auto-optimise-store` hardlinks them
+  (the two paths share inodes — `stat`-verified; `du` counts 639 MiB for the
+  pair vs ~620 for one). Only the wire can't dedupe. This is stamped on #120,
+  whose entire size table is closure arithmetic — without it, "drop the pin,
+  save 4 GiB" would have evaporated at the squashfs exactly like this did.
+- **Verified:** V0 flake check green; revert confirmed by closure (the plain
+  chromium is back, 9.38 GiB) rather than by reading the diff.
+- **Next suggestion:** #118 (smartd self-gate).
+
+## 2026-07-14 — #121: one chromium, not two — 687 MiB off every install (superseded by the revert above)
 - **Task:** BACKLOG #121, found by measuring #103's ISO delta. Nothing was
   failing — that is the point; a duplicate browser breaks no build.
 - **Did:** nixpkgs' chromium wrapper with `enableWideVine = true` (what the