Import the wilm endpoint telemetry, PC Detail rework and backup overlay

Ports 37 of Benjamin Baker's commits from the wilm branch, mirrored from the
corporate GitHub at 7905917c. wilm rides the publication lineage and shares no
ancestor with wj, so this is a filtered tree patch rather than a merge:
94 files, and every path the publication export strips (docs/, tools/, mcp/,
CLAUDE.md, start-*.sh, .gitea/, the three excluded tests) is held back, because
a raw diff would delete each of them from this tree.

What comes across:

* Endpoint telemetry, phase 2. Physical disk health from two sources, NIC link
  state, boot type, Defender health, processor/memory/chassis inventory, the
  listening TCP set, mapped network drives and Windows Update history. Five
  additive migrations, 0012 through 0016, off the 0011 head.
* Mapped drives are collected by a probe running in the interactive user's
  session, because they do not exist in the agent's session 0. Two Windows
  sources can disagree about one drive and the worse status wins, so a
  half-broken share is never rendered as healthy.
* Windows events are reported once each, keyed on the channel's own record id,
  instead of being re-sent whenever a report overlapped the last one.
* PC Detail rework: Details cards flow, the hand-written Network card gives way
  to a full address history, Storage and disk health merge into one card with
  two sections, Operator Reports and Corporate Tools get their own tabs.
* An opt-in restic backup overlay with a third container, restore gated on the
  dump's own data revision rather than the code head, and backup/restore history.
* The agent's version is read from the binary's PE version rather than trusted
  from the csproj, and the Fleet view gains an Agent Version column.
* The enqueue route now asks caller_holds instead of the owner's permissions,
  which closes the scoped-token elevation on run_script, update_app and
  system_restart.

Held back deliberately:

* agent/installer/install-shopdbagent.ps1 stays deleted, as upstream deleted it.
  The installer that reaches a bay is generated by _install_script() in
  plugins/endpoints/api/siteagent.py; the standalone script had stopped being
  shipped and was collecting fixes no endpoint ever ran.
* The .gitignore hunk adding docs/*.md. Correct on the publication lineage,
  where docs/ becomes the wiki and its absence is how the gates detect a
  published checkout. Here it would silently ignore every new doc.
* Their deletions of docs/DEV-BUILD-TEST.md and docs/PLUGIN-HOOKS.md. Upstream
  those were stubs; here PLUGIN-HOOKS.md is the 31KB document CLAUDE.md points
  readers at.
* Five zero-byte files committed by an accidental `git add -A`, a run log from
  the author's own machine, and docs/notes/, which is working scratch that says
  so in its own header and belongs in devnotes/ on this side.

Carried with the import so it lands green: the 17 new routes are described in
docs/api-inventory.json with the spec and project map regenerated, and two new
frontend specs read fixtures through fileURLToPath(URL) which node rejects under
jsdom's own URL global.

Suite 2591 passed / 9 skipped; frontend 391 passed; naming, style and doc gates
clean.

Scope: product

CONTRIBUTING.md

@@ -171,32 +171,15 @@ Tests are required for:
 
 ## Branches: what belongs on main, and what does not
 
-`main` is the curated product other sites adopt, and what the publication
-mirror exports. It is a release decision: something reaching `main` says other
-sites should take it. **`main` is not what this site runs.**
-
-Each branch answers to one instance:
-
-| branch | runs on | contains |
-|---|---|---|
-| `dev` | the dev instance | work being validated |
-| `wj` | this site's PRODUCTION | everything this site runs |
-| `main` | nothing directly | the curated release for other sites |
-| `wilm` | the other site | their work, on the corporate GitHub |
-
-So work flows `dev` -> `wj` -> `main`: land it on `dev`, validate it on the dev
-instance, take it to `wj` for production, and promote to `main` what you are
-happy for another site to run. Promoting first and back-filling the site branch
-is the wrong way round - it puts unvalidated work in front of other sites and
-leaves production behind.
-
-`wilm` is not visible from the dev box because that machine has no account on
-the corporate GitHub, which is why `fetch-wilm-branch.cmd` exists to bring it
-back for review. It sits on the publication lineage, so it shares no ancestor
-with `main`/`wj`/`dev` and cannot be merged locally.
+`main` is the product every site runs and the publication mirror exports.
+`<site>` branches hold work that is not ready for other sites to see. There are
+two: `wj` here, and `wilm` on the corporate GitHub, where the other site
+develops the .NET endpoint agent.
 
 A site branch is not a fork. Both feed `main`, and the sooner they do it the
-cheaper it is.
+cheaper it is. A branch the dev box cannot see is still a branch: `wilm` is not
+visible from here because this machine has no GitHub account, which is why
+`fetch-wilm-branch.cmd` on the share exists to bring it back for review.
 
 **Most work is product.** ADR-015 gives site differences three homes on `main`:
 a setting with a neutral default, seed data, or a site-namespaced directory