chore: remove AI session save/resume helpers

Drop the save-session/resume system entirely:

- functions/save_claude_session.fish, save_antigravity_session.fish
  (session-start hook scripts)
- functions/claude-resume.fish, antigravity-resume.fish, code-resume.fish
  (consumers of the .claude_session/.antigravity_session files)

Also updates docs/fish-config.md (removes the three function sections,
drops the session-helper mention from the python3 dependency note) and
docs/fish-config.index (removes the orphaned keyword entries). Generated
html/wiki/man are rebuilt by build-docs.yml on merge.

External hook registrations were removed from ~/.claude/settings.json and
~/.gemini/settings.json (the latter pointed at an already-deleted
save_gemini_session.fish); those files live outside this repo.

docs/fish-config.index

@@ -133,14 +133,11 @@ logging=## 5.11 Pager and Logging
 logs=### logs
 smart-exit=### smart_exit
 ai=## 5.12 AI and Developer Tools
-antigravity=### antigravity-resume
 antigravity-ide=### antigravity-ide
 agy=### agy
 claude-cli=### claude
-claude=### claude-resume
 claude-docs=### claude-docs
 claude-pr=### claude-pr
-code-resume=### code-resume
 superpowers=### superpowers
 media=## 5.13 Media and Utilities
 dng2avif=### dng2avif

docs/fish-config.md

@@ -1124,13 +1124,6 @@ Add -i (interactive confirmation) to destructive commands:
     Synopsis:  antigravity-ide [args...]
     Runs the antigravity-ide editor with warnings filtered.
 
-### antigravity-resume
-
-    Synopsis:  antigravity-resume
-    Resumes the most recent Antigravity session from the .antigravity_session
-    file in the current directory, or opens an interactive fzf picker if no
-    session file is found.
-
 ### agents-init
 
     Synopsis:  agents-init [--agents | --plugins]
@@ -1163,12 +1156,6 @@ Add -i (interactive confirmation) to destructive commands:
     claude
     claude --resume
 
-### claude-resume
-
-    Synopsis:  claude-resume
-    Resumes the most recent Claude Code session from the .claude_session
-    file in the current directory, or opens an interactive fzf picker.
-
 ### claude-docs
 
     Synopsis:  claude-docs
@@ -1182,12 +1169,6 @@ Add -i (interactive confirmation) to destructive commands:
     conventional commit, verification, push, and open a PR with a manual
     verification checklist.
 
-### code-resume
-
-    Synopsis:  code-resume
-    Resumes the most recent AI session (Claude or Antigravity), preferring
-    the newest session file found in the current directory.
-
 ### superpowers
 
     Synopsis:  superpowers [on|off] [-g]
@@ -1471,11 +1452,10 @@ fish-deps manages these tools. Run `fish-deps` to check status, or
     trash       Safe delete (trash-cli)
     kitty       GPU-accelerated terminal (primary)
     wezterm     GPU-accelerated terminal (alternative)
-    python3     Standalone interpreter — used by the AI session helpers
-                (save_claude_session / save_antigravity_session) and the
-                paru/yay log cleaner. Note: uv does not provide python3 on
-                PATH, and Arch's base does not include it, so it is listed
-                separately. All consumers degrade gracefully without it.
+    python3     Standalone interpreter — used by the paru/yay log cleaner.
+                Note: uv does not provide python3 on PATH, and Arch's base
+                does not include it, so it is listed separately. All
+                consumers degrade gracefully without it.
 
 ## Install Methods