Propose Lot 21: windows-rs 0.100, once windows itself ships

.claude/skills/upgrade-dependencies/SKILL.md

@@ -30,14 +30,17 @@ what to take.
 ## 2. One dependency at a time
 
 On `deps-YYYY-MM-DD`, from `main`, one commit per dependency, or per family
-that moves together (`windows` and `windows-registry`):
+that moves together. The windows-rs crates (`windows`, `windows-registry`)
+are one family: one does not move without the other ([Lot 21](../../../docs/design/21-windows-rs-0100.md)).
 
 1. **Read the upgrade path first**: the changelog, release notes or migration
    guide of every version between the locked one and the target, from the
    publisher — the crate's repository, docs.rs, the action's releases. Note
    each breaking change this code meets.
 2. Raise the requirement in `Cargo.toml`, or the tag in the workflow, then
-   `cargo update -p <crate>`.
+   `cargo update -p <crate>`. A dependency that needs a newer Rust than
+   `rust-version` raises `rust-version` in the same commit; it is never held
+   back for that.
 3. Fix each break **the way the guide says**: the new API, the replacement it
    names. Never: a lint silenced (`#[allow(deprecated)]` and the like), a
    `[patch]` or a fork, a version held below the target, the old code copied

docs/design/20-build-chain.md

@@ -1,7 +1,8 @@
 # Lot 20 — The build chain, official and kept current
 
-**Status: decided 2026-10-17; part 1 built the same day**, its attestation to
-be seen at the next release. Taken while Lot 19's spike waits for an Office
+**Status: decided and built 2026-10-17.** Seen the same day: Dependabot's
+first PR, two crate patches, merged itself once CI had passed. Still to see:
+an update that waits for the maintainer, and the first attested release. Taken while Lot 19's spike waits for an Office
 update. Two parts, in this order: Dependabot keeps current whatever the first
 part settles on.
 

docs/design/21-windows-rs-0100.md

@@ -0,0 +1,46 @@
+# Lot 21 — Moving to windows-rs 0.100
+
+**Status: proposed 2026-10-17, waiting for `windows` 0.100 on crates.io.**
+windows-rs moved its smaller crates to 0.100.0 on 2026-09-03 (its release
+74) and held back `windows` and `windows-sys` while it tests their new
+metadata ([microsoft/windows-rs#4867](https://github.com/microsoft/windows-rs/issues/4867)).
+The program uses `windows` 0.62 throughout and `windows-registry` 0.6; they
+move together, once, following the `upgrade-dependencies` skill.
+
+## Why a lot of its own
+
+The 0.100 bindings come from the Windows SDK headers instead of the
+Win32Metadata project, and the publisher lists what that breaks:
+
+- features and modules renamed after SDK headers (`Win32_*` become lowercase
+  header names): every feature in `Cargo.toml` and every import;
+- signatures as the headers declare them: raw pointer and count parameters,
+  `BOOL` and `HRESULT` returned as such;
+- generated enum and ownership types removed where the SDK has primitives —
+  `HLOCAL`, for one, no longer frees itself;
+- record layouts as the headers lay them out.
+
+Nearly every `unsafe` call and its `// SAFETY:` comment is touched, so this is
+the riskiest dependency change the program has had.
+
+## Until then
+
+`windows-registry` stays at 0.6. Tried on 2026-10-17: 0.100 builds with no
+change to the code and adds about 1.5 KB, but brings a second generation of
+`windows-result`, `windows-strings` and `windows-link` beside the ones
+`windows` 0.62 uses, and needs Rust 1.95 where `rust-version` says 1.88 —
+for nothing the program uses. Decided with the maintainer the same day: wait.
+
+## When `windows` 0.100 lands
+
+- Read the publisher's migration notes and the crates' documentation first.
+- One commit per area of the program, each through `build.ps1 test`; no
+  workaround, as the skill says. `rust-version` follows the family's minimum.
+- In the field, every path that calls Windows: detection and the presence
+  writer's wait, the games marked by hand, the GPU counters, the icon, menu
+  and notifications, the session end, the update and `purge`.
+- The watcher measured at rest and in a game against 0.4.0.
+
+**Done when** the program builds on `windows` and `windows-registry` 0.100
+with no crate of the 0.62 generation left, every check passes, a field
+session has exercised each path above, and the footprint is recorded.

docs/design/README.md

@@ -30,7 +30,8 @@ the pages keep the history.
 | 17 | [A log that turns over each day](17-log-rotation.md) | done 2026-09-26; the zip's update path to see at the next release |
 | 18 | [When the game is gone and nobody is there](18-game-gone-nobody-there.md) | proposed, not decided |
 | 19 | [Starting from Windows' Startup list](19-startup-list.md) | proposed; a spike first |
-| 20 | [The build chain, official and kept current](20-build-chain.md) | part 1 built 2026-10-17; Dependabot next |
+| 20 | [The build chain, official and kept current](20-build-chain.md) | built 2026-10-17; the first wait and the first attested release to see |
+| 21 | [Moving to windows-rs 0.100](21-windows-rs-0100.md) | proposed; waiting for `windows` 0.100 |
 
 Logging came before the icon, so the icon was written in the final log
 vocabulary; the windowless build came before it too, so the window and message