docs(readme): drop manual-install fallback, explain --path for Gemini CLI

Manual symlink instructions added noise to the install section.
Users who need that flow can read the Codex section (same pattern,
different path). For Gemini, called out why our install command
uses '--path skills/openkb': the repo root holds the openkb Python
package, not the skill, so the installer needs to be pointed at
the skill subdirectory.

Author: KylinMountain

README.md

@@ -258,7 +258,7 @@ To remove later: `/plugin uninstall openkb` then `/plugin marketplace remove Vec
 
 #### Gemini CLI
 
-Native skills installer fetches a single skill folder from a Git repo:
+Native [skills installer](https://geminicli.com/docs/cli/skills/) fetches the skill folder from this repo. `--path skills/openkb` points it at the sub-directory containing `SKILL.md` (the rest of the repo is the openkb codebase, not skill content):
 
 ```bash
 gemini skills install https://github.com/VectifyAI/OpenKB.git --path skills/openkb --consent
@@ -276,19 +276,6 @@ ln -s ~/openkb-src/skills/openkb ~/.agents/skills/openkb
 
 Codex discovers skills under `.agents/skills/` walking up from cwd, or `~/.agents/skills/` for user-scope. To update later: `cd ~/openkb-src && git pull`.
 
-#### Manual install (any agent)
-
-If you don't want to use any installer, just drop the skill folder into the agent's user-scope skills directory:
-
-```bash
-# Claude Code
-ln -s "$(pwd)/skills/openkb" ~/.claude/skills/openkb
-# Gemini CLI
-ln -s "$(pwd)/skills/openkb" ~/.gemini/skills/openkb
-# Codex
-ln -s "$(pwd)/skills/openkb" ~/.agents/skills/openkb
-```
-
 #### After install
 
 When you ask about content in an OpenKB knowledge base, the skill activates and points the agent at `openkb status` to discover the KB root, `openkb list` for the document catalog, and direct Markdown reads for concept and summary content. The skill is read-only: it won't run `openkb add`, `remove`, or `lint --fix` without you asking. See [`skills/openkb/SKILL.md`](skills/openkb/SKILL.md) for the full instruction set the agent receives.