fix(wiki): purge through the plugin page actions and count reset deletions (#101)

Closes #99. Closes #100.

## #99 — purge used the core topic API

`deploy-wiki --stale-policy purge` deleted pages with `DELETE /api/v3/topics/{tid}`. On a NodeBB running `nodebb-plugin-westgate-wiki` that is refused for topics in wiki categories — revision history is plugin-owned — so every purge failed with HTTP 400 and the deploy exited 1.

Purge now goes through the plugin's own page actions:

1. `PUT /api/v3/plugins/westgate-wiki/page/tombstone`
2. `DELETE /api/v3/plugins/westgate-wiki/page/hard-purge`

in that order, because a page must be tombstoned before it can be purged. A page that is already gone answers 404 on the tombstone and is treated as a completed purge, as before.

**Archive was audited and needs no change.** It rewrites the page through `updatePost`, which is an ordinary post edit the plugin allows; only delete, restore, and purge are reserved to the page actions.

**The wiki home topic.** A namespace reset enumerates every topic in the category, including the home page, which the plugin excludes from tombstone, restore, and purge alike. Those are now skipped instead of aborting the reset. NodeBB answers 403 for that and for a token without purge privileges alike, and the response body cannot tell the two apart — what can is scope. A category where nothing at all could be deleted is a privilege problem, so the run still fails there rather than writing a manifest that claims a fresh start over pages that are all still present.

**The fakes.** Every fake NodeBB in `wiki_deploy_test.go` now goes through one constructor that refuses native topic mutation exactly the way the plugin does. The old fakes answered the core API, which is how a purge path that has never worked in production stayed green in CI.

## #100 — `stale: 0` above `purged: 1213`

The reset purge never went through stale computation, so the preview reported zero deletions on a run that would delete every topic in the managed categories.

Reset deletions are now counted in `stale`, which is the number callers word their destructive-policy warning around, and the summary gains a line naming the reset and how many of its targets the manifest has no record of writing:

```
stale:       1213
purged:      1213
namespace reset: 1213 (unrecognized: 13)
  unrecognized pages were not written by this deployer; recreating them is not possible
```

The unrecognized subset is the number worth surfacing, since those are the deletions a re-seed cannot undo. The `--reset-managed-namespaces` help text now says plainly that the flag deletes every page in the managed categories, not only the ones this deployer wrote.

`DeployResult` is exported so the console reads named fields instead of eleven positional ints.

## Verification

`go vet ./...` and `go test ./...` pass. New tests cover the plugin purge order, the already-missing page, the skipped undeletable topic, the per-category privilege failure, and the reset counts.Reviewed-on: #101

Co-authored-by: vickydotbat <vickydotbat@tutamail.com>

internal/dispatch/dispatch.go

@@ -289,7 +289,8 @@ var Registry = []Builder{
 					"--dry-run                        report changes without writing",
 					"--create                         allow missing pages to be created",
 					"--force                          update unchanged pages",
-					"--reset-managed-namespaces       reset managed namespace state",
+					"--reset-managed-namespaces       delete every page in the managed categories, including",
+					"                                 pages this deployer never wrote, then recreate from source",
 				},
 				Aliases: []CommandAlias{{Name: "deploy-wiki"}},
 			},