fix(sl): correct reserved-word/week-grain SQL and classify sl_query errors (#340)

Reserved-word columns (like, default, ...) referenced as source.col were
quoted with postgres double quotes even on BigQuery/MySQL, where a
double-quoted token is a string literal, not an identifier -- the
"Unexpected string literal" semantic-layer errors. quote_reserved_identifiers
now uses the identifier quote char of the dialect it will be parsed in
(backtick for BigQuery/MySQL), threaded through the planner and generator
parse sites; week_<weekday> granularity now emits WEEK(<weekday>) on BigQuery
instead of the invalid WEEK_MONDAY.

On the telemetry side, warehouse rejections from the sl_query execution path
are classified as expected (KtxQueryError) via a new shared markExpected()
helper, so routine agent/warehouse query failures stop reaching PostHog Error
Tracking as ktx faults; the sql_execution catch is refactored onto the same
helper. The daemon-compile boundary is deliberately left unclassified here so
genuine daemon crashes stay visible.

python/ktx-sl/semantic_layer/duplicate_check.py

@@ -42,7 +42,7 @@ def validate_measure_duplicates(
         parsed: list[tuple[str, exp.Expression | None, str | None, frozenset[str]]] = []
         for m in source.measures:
             try:
-                quoted = quote_reserved_identifiers(m.expr)
+                quoted = quote_reserved_identifiers(m.expr, dialect)
                 tree = sqlglot.parse_one(f"SELECT {quoted}", read=dialect)
                 expr_node = tree.expressions[0] if tree.expressions else None
             except Exception: