docs: README hook, discoverability, Pages site, game-behaviour reference

- README: lead with what it is + the AI-agent-collaboration research
  framing + current status in the first paragraph; rename H1 to
  "GoldenEye 007 PC Port"; add a live CI badge.
- New "How this differs from the other GoldenEye PC projects" section:
  this is a source port of the N64 original; the Recomp projects
  binary-translate the Xbox 360 XBLA remaster (different game, no shared
  code).
- CITATION.cff for GitHub's "Cite this repository" widget / Zenodo.
- GitHub Pages site off /docs (_config.yml + index.md landing page).
- agentic-development.md: searchable title + abstract.
- .github/social-preview.{png,html,md}: repo social-preview card styled
  after the GE mission-briefing screen, kept editable (CSS source + a
  regen/how-to doc beside the PNG).
- docs/dev/game-behavior-reference.md: distilled the raw GameFAQs
  walkthrough dump down to the behaviour-defining parts (combat/AI model,
  difficulty scaling, per-level objective sets, timers, weapon data,
  original-game quirks). Credits: Brett "Nemesis" Franklin, marshmallow.

Claude-Session: https://claude.ai/code/session_01GULf6knbsqfsnW39tMr9WT

docs/_config.yml

@@ -0,0 +1,16 @@
+# GitHub Pages config. Site is served from the /docs folder on the default
+# branch (Settings -> Pages -> Deploy from a branch -> main / docs).
+title: GoldenEye 007 PC Port
+description: >-
+  A native PC port of the original Nintendo 64 GoldenEye 007, built from its
+  decompiled source, and a case study in AI-agent collaboration on a large
+  low-level codebase.
+theme: jekyll-theme-cayman
+show_downloads: false
+
+# jekyll-relative-links (on by default for Pages) rewrites the .md links in
+# these docs to .html so cross-links work on the published site.
+
+# Rolling local working files - not useful as published pages.
+exclude:
+  - HANDOFF.md