fix(diagnostics): sqlite3 probe with login-PATH + candidate fallback (#19)

@cmalpass's April 25 follow-up on #19: diagnostics reported "sqlite3
not installed or on system PATH" while sqlite3 was actually installed
and Hermes was using it fine. Same false-negative class the `hermes`
probe pre-fix had — a bare `command -v sqlite3` in the non-login SSH
shell misses installs at /opt/homebrew/bin or /usr/local/bin when
the user's PATH export lives in .zprofile (the typical Homebrew
setup). The hermes probe was upgraded to source rc files + walk a
candidate list; sqlite3 wasn't.

Mirror the same pattern:

- Move the sqlite3 detection AFTER the rc-source loop so the login
  PATH is in scope.
- Add a standard-location fallback list:
  /usr/bin/sqlite3, /usr/local/bin/sqlite3,
  /opt/homebrew/bin/sqlite3, /opt/local/bin/sqlite3.
- Use the resolved sqlite3 binary explicitly in the
  sqlite3CanOpenStateDB probe so it doesn't re-fail-by-PATH when the
  binary is at e.g. /opt/homebrew/bin. Falls back to bare `sqlite3`
  so the FAIL detail line still carries the real error.

Hermes non-login probe stays as-is — that semantic ("is hermes on
the un-enriched PATH?") is meaningful and we don't want to muddle it.

Failure-hint copy on sqlite3Installed updated to spell out the new
fallback behavior so users who still see FAIL get accurate guidance
(install via package manager, OR symlink an existing binary into a
location the probe checks).

Closes the third and last open layer of #19. Layer 1 (104-byte
ControlMaster path) was fixed in v2.0.2; layer 2 (pill / diagnostics
disagreement) was fixed in v2.5.1 (#44). Ships in v2.5.2.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scarf/scarf/Features/Servers/ViewModels/RemoteDiagnosticsViewModel.swift

@@ -79,7 +79,7 @@ final class RemoteDiagnosticsViewModel {
             case .stateDBReadable:
                 return "Scarf can't read `state.db` — Sessions, Activity, Dashboard stats all depend on this. Same fix pattern as config.yaml."
             case .sqlite3Installed:
-                return "Scarf pulls a snapshot of state.db via `sqlite3 .backup`, so sqlite3 must be installed on the remote. Install: `sudo apt install sqlite3` (Ubuntu/Debian), `sudo yum install sqlite` (RHEL/Fedora), `apk add sqlite` (Alpine)."
+                return "Scarf pulls a snapshot of state.db via `sqlite3 .backup`, so sqlite3 must be installed on the remote AND visible to non-interactive SSH sessions. The probe sources `~/.zshenv` / `.zprofile` / `.bash_profile` / `.profile` and falls back to `/usr/bin`, `/usr/local/bin`, `/opt/homebrew/bin`, and `/opt/local/bin` — if it's still not found, either install via your package manager (`sudo apt install sqlite3` / `sudo yum install sqlite` / `apk add sqlite`) or symlink the existing binary into a location the probe checks (e.g. `sudo ln -s /your/path/sqlite3 /usr/local/bin/sqlite3`)."
             case .sqlite3CanOpenStateDB:
                 return "sqlite3 exists but can't open state.db. Could be a permission issue, a corrupt DB, or a version skew."
             case .hermesBinaryNonLogin:
@@ -238,21 +238,10 @@ final class RemoteDiagnosticsViewModel {
             fi
         fi
 
-        if command -v sqlite3 > /dev/null 2>&1; then
+        # Non-login PATH probe for `hermes` runs in the bare shell BEFORE
-            sq=$(command -v sqlite3)
+        # sourcing rc files — that semantic ("is hermes on the un-enriched
-            emit sqlite3Installed PASS "$sq"
+        # PATH the SSH session inherits?") is meaningful and we don't
-        else
+        # want to muddle it.
-            emit sqlite3Installed FAIL "sqlite3 not on PATH"
-        fi
-
-        if sqlite3 "$H/state.db" 'SELECT 1' > /dev/null 2>&1; then
-            emit sqlite3CanOpenStateDB PASS ""
-        else
-            err=$(sqlite3 "$H/state.db" 'SELECT 1' 2>&1 | head -1)
-            emit sqlite3CanOpenStateDB FAIL "$err"
-        fi
-
-        # Non-login PATH: just ask the current shell.
         hpath=$(command -v hermes 2>/dev/null)
         if [ -n "$hpath" ]; then
             emit hermesBinaryNonLogin PASS "$hpath"
@@ -260,10 +249,18 @@ final class RemoteDiagnosticsViewModel {
             emit hermesBinaryNonLogin FAIL "not on non-login PATH ($PATH)"
         fi
 
-        # Login PATH: source rc files (mirroring TestConnectionProbe) and re-probe.
+        # Source rc files (mirroring TestConnectionProbe) so subsequent
+        # probes see the user's full login PATH. sqlite3 / hermes-login
+        # detection happens AFTER this so installs in Homebrew /
+        # `/usr/local/bin` / pipx / etc. are findable on hosts where the
+        # non-login SSH session inherits a stripped PATH (issue #19,
+        # @cmalpass's case where sqlite3 was installed but probed as
+        # missing — the non-login shell didn't have Homebrew on PATH).
         for rc in "$HOME/.zshenv" "$HOME/.zprofile" "$HOME/.bash_profile" "$HOME/.profile"; do
             [ -f "$rc" ] && . "$rc" 2>/dev/null
         done
+
+        # Login-PATH `hermes` probe with hardcoded candidate fallback.
         hpath2=$(command -v hermes 2>/dev/null)
         if [ -z "$hpath2" ]; then
             for cand in "$HOME/.local/bin/hermes" "/opt/homebrew/bin/hermes" "/usr/local/bin/hermes" "$HOME/.hermes/bin/hermes"; do
@@ -276,6 +273,36 @@ final class RemoteDiagnosticsViewModel {
             emit hermesBinaryLogin FAIL "not found after sourcing rc files"
         fi
 
+        # sqlite3 detection — also after sourcing rc files, with a
+        # standard-location fallback that mirrors the hermes probe
+        # above. Pre-fix this was a bare `command -v sqlite3` in the
+        # non-login shell, which produced false negatives on Homebrew
+        # / `/usr/local/bin` installs (issue #19 layer 3).
+        sqbin=$(command -v sqlite3 2>/dev/null)
+        if [ -z "$sqbin" ]; then
+            for cand in "/usr/bin/sqlite3" "/usr/local/bin/sqlite3" "/opt/homebrew/bin/sqlite3" "/opt/local/bin/sqlite3"; do
+                if [ -x "$cand" ]; then sqbin="$cand"; break; fi
+            done
+        fi
+        if [ -n "$sqbin" ]; then
+            emit sqlite3Installed PASS "$sqbin"
+        else
+            emit sqlite3Installed FAIL "not found on PATH or in standard locations"
+        fi
+
+        # Use the resolved sqlite3 path explicitly so the open-state.db
+        # probe doesn't re-fail-by-PATH when the binary is at e.g.
+        # /opt/homebrew/bin. Falls back to bare `sqlite3` so the FAIL
+        # detail line (with the underlying error) is still informative
+        # if no candidate was found.
+        sqcmd="${sqbin:-sqlite3}"
+        if "$sqcmd" "$H/state.db" 'SELECT 1' > /dev/null 2>&1; then
+            emit sqlite3CanOpenStateDB PASS ""
+        else
+            err=$("$sqcmd" "$H/state.db" 'SELECT 1' 2>&1 | head -1)
+            emit sqlite3CanOpenStateDB FAIL "$err"
+        fi
+
         if command -v pgrep > /dev/null 2>&1; then
             emit pgrepAvailable PASS "$(command -v pgrep)"
         else