feat(skills): add project-level sf-wiki skill override with UPPERCASE convention

.sf/skills/ is the project-local skill override directory. This override
inherits all sf-wiki defaults and adds one project-specific rule: wiki
pages use UPPERCASE filenames (INDEX.md, ARCHITECTURE.md, etc.) to match
the .sf/ operational file convention (DECISIONS.md, KNOWLEDGE.md, etc.).

The built-in src/resources/skills/sf-wiki/SKILL.md stays generic (lowercase).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.sf/skills/sf-wiki/SKILL.md

@@ -0,0 +1,59 @@
+---
+name: sf-wiki
+description: Build a sparse SF-native codebase wiki or subsystem map. Use inside autonomous workflow when SF needs durable repo orientation, architecture maps, or generated reference docs.
+---
+
+# SF Wiki
+
+Use this skill to generate compact repository documentation for future agents and
+humans. The output is an SF-native codebase map, not a Factory upload.
+
+## Output
+
+Default location:
+
+- `.sf/wiki/` for runtime working context.
+- `docs/generated/wiki/` only when the user wants tracked generated docs.
+
+Prefer `.sf/wiki/` for autonomous workflow context so tracked docs stay sparse.
+
+## Survey
+
+Use two passes:
+
+1. Structural: README, AGENTS, package manifests, build/test config, docs,
+   entrypoints, CI, and top-level directories.
+2. Source: routes, commands, providers, services, workflows, tests, generated
+   artifacts, and feature flags.
+
+Reconcile source-derived topics with directory enumeration. If a non-trivial
+directory is skipped, record the reason in one sentence.
+
+## Pages
+
+Keep the wiki small by default. **This project uses UPPERCASE filenames** to
+match the `.sf/` operational file convention (DECISIONS.md, KNOWLEDGE.md, etc.):
+
+- `INDEX.md`: what this repo is, how to run it, where to start.
+- `ARCHITECTURE.md`: major subsystems and data/control flow.
+- `WORKFLOWS.md`: build, test, release, autonomous/SF flows.
+- `SUBSYSTEMS.md`: table of subsystem, path, purpose, owner signal, tests.
+- `GLOSSARY.md`: project terms only.
+
+Add subsystem pages only when the table would become unreadable.
+
+## Style
+
+- Optimize for context reload, not publication.
+- Use bullets and tables.
+- Link to canonical docs instead of copying them.
+- Avoid prose history unless it changes how someone should work.
+- Mark stale or uncertain facts explicitly.
+
+## Verification
+
+Before finishing:
+
+- Check every referenced path exists or is intentionally historical.
+- Run cheap repo discovery commands again if files changed during the scan.
+- Leave a short freshness note with date, commit, and commands used.