Canonical Wiki Paths Enforcement (#6)

### Summary
- Change generated topdata wiki links to target public wiki namespace and canonical slug paths.
- Add generated public path metadata to wiki page generation and page-index output.
- Add YAML-driven generated slug overrides and public-target collision validation.

### Details
- Generated relation links now render public targets such as:
  - `[[feat/hardiness-vs-enchantments|Hardiness vs. Enchantments]]`
  - `[[feat/favored-enemy-elves|Favored Enemy: Elves]]`
- Topdata page IDs remain the internal identity for output layout, managed markers, deploy state, and bookkeeping.
- Generated managed markers now include the effective public slug:
  - `<!-- sow-topdata-wiki:page=... wiki_slug=... -->`
- Page-index entries now include:
  - `public_slug`
  - `public_target`
- Added parsing and validation for `page_paths.slug_overrides` from `topdata/wiki/wiki.yaml`.
- Generated public targets are validated for duplicate namespace-local collisions.
- Table link helpers now derive public targets from target page titles when available, so display aliases do not accidentally change link destinations.

### Tests
- Added and updated coverage for:
  - public target rendering
  - marker `wiki_slug` output
  - page-index public metadata
  - duplicate generated public target rejection
  - slug override parsing and validation
  - override-driven target selection
  - target title slugging independent of display labels

### Validation
- `go test ./...`
- `gofmt -w` on changed Go files
- `./build-tool.sh`
- `git diff --check`

Reviewed-on: https://gitea.westgate.pw/ShadowsOverWestgate/sow-tools/pulls/6
Co-authored-by: vickydotbat <vickydotbat@tutamail.com>
Co-committed-by: vickydotbat <vickydotbat@tutamail.com>

internal/topdata/wiki_tables.go

@@ -813,8 +813,10 @@ func (p *wikiExprParser) callHelper(name string, args []any) (any, error) {
 			if p.ctx != nil && !p.ctx.canReferenceWikiKey(key) {
 				return "", nil
 			}
-			if pageID := wikiPageIDForKey(key); pageID != "" {
-				key = pageID
+			if p.ctx != nil {
+				if target := p.ctx.publicWikiTargetForKey(key, ""); target != "" {
+					key = target
+				}
 			}
 			return "[[" + key + "]]", nil
 		}
@@ -827,8 +829,10 @@ func (p *wikiExprParser) callHelper(name string, args []any) (any, error) {
 			if p.ctx != nil && !p.ctx.canReferenceWikiKey(key) {
 				return "", nil
 			}
-			if pageID := wikiPageIDForKey(key); pageID != "" {
-				key = pageID
+			if p.ctx != nil {
+				if target := p.ctx.publicWikiTargetForKey(key, label); target != "" {
+					key = target
+				}
 			}
 			return "[[" + key + "|" + label + "]]", nil
 		}