feat(skills): blank-slate skills — install --no-skills + opt-out/opt-in (#36228)

* feat(install): --no-skills flag for blank-slate default profile

Add an install-time --no-skills flag so the default ~/.hermes profile can
be created with zero bundled skills, matching what
`hermes profile create --no-skills` already does for named profiles.

The flag writes $HERMES_HOME/.no-bundled-skills and skips the install-time
seed. sync_skills() now honors that marker with an early return
(skipped_opt_out=True), so neither the installer, a later `hermes update`,
nor a direct sync re-injects bundled skills into a profile that opted out.

Previously the marker was only checked by seed_profile_skills() (named
profiles); the default profile had no opt-out and `hermes update` would
re-seed it every time.

Tests: TestNoBundledSkillsOptOut covers marker-present (no-op) and
marker-absent (normal seed) paths.

* feat(skills): hermes skills opt-out / opt-in for existing profiles

Adds an interactive counterpart to the install-time --no-skills flag so
an already-installed profile (default or named) can toggle the
.no-bundled-skills marker without reinstalling.

- `hermes skills opt-out` writes the marker (stop future seeding). Safe
  by default: nothing on disk is touched.
- `hermes skills opt-out --remove` ALSO deletes already-present bundled
  skills, but ONLY ones that are manifest-tracked AND byte-identical to
  their origin hash. User-edited bundled skills, hub-installed skills, and
  hand-written skills are never removed. Previews + confirms before
  deleting (--yes to skip).
- `hermes skills opt-in [--sync]` removes the marker and optionally
  re-seeds immediately.

Core logic lives in tools/skills_sync.py (set_bundled_skills_opt_out,
is_bundled_skills_opt_out, remove_pristine_bundled_skills) reusing the
existing manifest origin-hash machinery for the safety check.

Tests: TestOptOutToggleAndRemove covers marker toggle idempotency and
proves user-modified + non-bundled skills survive --remove.

* docs: blank-slate skills — install --no-skills + opt-out/opt-in

- features/skills.md: new 'Starting with a blank slate' section covering
  the install flag, profile-create flag, and runtime opt-out/opt-in, with
  a safe-by-default note.
- reference/cli-commands.md: document the new skills opt-out / opt-in
  subcommands + examples.
- reference/profile-commands.md: fix the marker filename (was .no-skills,
  actually .no-bundled-skills) and cross-link the runtime commands.

Validated with a full docusaurus build (exit 0); the three edited pages
compile clean with no new warnings.

scripts/install.sh

@@ -70,6 +70,7 @@ DETECTED_BROWSER_EXECUTABLE=""
 USE_VENV=true
 RUN_SETUP=true
 SKIP_BROWSER=false
+NO_SKILLS=false
 BRANCH="main"
 INSTALL_COMMIT=""
 ENSURE_DEPS=""
@@ -104,6 +105,10 @@ while [[ $# -gt 0 ]]; do
             SKIP_BROWSER=true
             shift
             ;;
+        --no-skills)
+            NO_SKILLS=true
+            shift
+            ;;
         --branch|-Branch)
             BRANCH="$2"
             shift 2
@@ -158,6 +163,9 @@ while [[ $# -gt 0 ]]; do
             echo "  --no-venv      Don't create virtual environment"
             echo "  --skip-setup   Skip interactive setup wizard"
             echo "  --skip-browser Skip Playwright/Chromium install (browser tools won't work)"
+            echo "  --no-skills    Start with a blank slate — seed no bundled skills, and"
+            echo "                   write \$HERMES_HOME/.no-bundled-skills so future"
+            echo "                   'hermes update' runs never inject bundled skills either"
             echo "  --branch NAME  Git branch to install (default: main)"
             echo "  --commit SHA   Pin checkout to a specific commit after clone/update"
             echo "  --manifest     Print desktop bootstrap stage manifest as JSON"
@@ -1767,14 +1775,26 @@ SOUL_EOF
     log_success "Configuration directory ready: ~/.hermes/"
 
     # Seed bundled skills into ~/.hermes/skills/ (manifest-based, one-time per skill)
-    log_info "Syncing bundled skills to ~/.hermes/skills/ ..."
-    if "$INSTALL_DIR/venv/bin/python" "$INSTALL_DIR/tools/skills_sync.py" 2>/dev/null; then
-        log_success "Skills synced to ~/.hermes/skills/"
+    if [ "$NO_SKILLS" = true ]; then
+        # Blank-slate install: write the opt-out marker and skip seeding.
+        # skills_sync.py and `hermes update` both honor this marker, so the
+        # default profile stays empty across future updates too.
+        printf '%s\n' \
+            "This profile opted out of bundled-skill seeding (installed with --no-skills)." \
+            "Delete this file to re-enable sync on the next 'hermes update'." \
+            > "$HERMES_HOME/.no-bundled-skills" 2>/dev/null || true
+        log_info "Skipping bundled skills (--no-skills). Wrote $HERMES_HOME/.no-bundled-skills"
+        log_info "  Future 'hermes update' runs will not inject bundled skills. Delete the marker to opt back in."
     else
-        # Fallback: simple directory copy if Python sync fails
-        if [ -d "$INSTALL_DIR/skills" ] && [ ! "$(ls -A "$HERMES_HOME/skills/" 2>/dev/null | grep -v '.bundled_manifest')" ]; then
-            cp -r "$INSTALL_DIR/skills/"* "$HERMES_HOME/skills/" 2>/dev/null || true
-            log_success "Skills copied to ~/.hermes/skills/"
+        log_info "Syncing bundled skills to ~/.hermes/skills/ ..."
+        if "$INSTALL_DIR/venv/bin/python" "$INSTALL_DIR/tools/skills_sync.py" 2>/dev/null; then
+            log_success "Skills synced to ~/.hermes/skills/"
+        else
+            # Fallback: simple directory copy if Python sync fails
+            if [ -d "$INSTALL_DIR/skills" ] && [ ! "$(ls -A "$HERMES_HOME/skills/" 2>/dev/null | grep -v '.bundled_manifest')" ]; then
+                cp -r "$INSTALL_DIR/skills/"* "$HERMES_HOME/skills/" 2>/dev/null || true
+                log_success "Skills copied to ~/.hermes/skills/"
+            fi
         fi
     fi
 }