fix(continuous-learning): bump observer MAX_TURNS default to 50 (#2035)

The observer's MAX_TURNS default of 20 was systematically insufficient
for the MAX_ANALYSIS_LINES default of 500. First-cycle analysis on a
fresh project consistently failed with "Reached max turns (20)", forcing
users to either raise ECC_OBSERVER_MAX_TURNS or lower
ECC_OBSERVER_MAX_ANALYSIS_LINES before the observer became useful.

Pair the defaults so the out-of-the-box experience succeeds: bump
MAX_TURNS to 50 (the value the reporter empirically settled on for the
500-line default). The safety floor (turns < 4 falls back to default) is
preserved.

Test asserting the default constant is updated alongside the source.

skills/continuous-learning-v2/agents/observer-loop.sh

@@ -170,17 +170,20 @@ Rules:
 PROMPT
 
   timeout_seconds="${ECC_OBSERVER_TIMEOUT_SECONDS:-120}"
-  max_turns="${ECC_OBSERVER_MAX_TURNS:-10}"
+  # Default MAX_TURNS=50 to pair with the MAX_ANALYSIS_LINES=500 default (#2035).
+  # A 500-observation batch consistently exhausted the previous 20-turn budget,
+  # forcing every first-cycle analysis to fail with "Reached max turns".
+  max_turns="${ECC_OBSERVER_MAX_TURNS:-50}"
   exit_code=0
 
   case "$max_turns" in
     ''|*[!0-9]*)
-      max_turns=10
+      max_turns=50
       ;;
   esac
 
   if [ "$max_turns" -lt 4 ]; then
-    max_turns=10
+    max_turns=50
   fi
 
   # Ensure CWD is PROJECT_DIR so the relative analysis_relpath resolves correctly