Keep tippecanoe's own errors from being reported as protobuf errors

A tile that fails to decode is reported with EXIT_MVT, while a tile that
protozero throws on is reported with EXIT_PROTOBUF. Now that decoding
failures are raised as a tippecanoe_error rather than exiting on the
spot, the catch that was written for protozero's exceptions catches
tippecanoe's own as well, since tippecanoe_error is a std::exception:
mvt_tile::decode() throwing "Tile decompression failed" came back out as
EXIT_PROTOBUF and "PBF decoding error in tile z/x/y".

Catch tippecanoe_error first at the four places that wrap a decode in a
try. In overzoom() and in tippecanoe-decode it can be rethrown for
main() to report. In tile-join it can't: append_tile() runs on a worker
thread, where an escaping exception would call std::terminate() instead
of exiting, so report it and exit with its own status there.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DuCSVGssWNUCpVEE8Yp5HT

CHANGELOG.md

@@ -8,6 +8,11 @@
   before. Along the way this fixes a leaked `z_stream` when `compress()`
   failed and two `exit()` calls that could run from a destructor or from
   `mvt_value`'s hash function.
+* Keep reporting a tile that fails to decode as `EXIT_MVT`, and report why.
+  Now that decoding failures throw, the `catch` meant for protozero's
+  exceptions was catching tippecanoe's own as well, replacing their exit
+  status and message with `EXIT_PROTOBUF` and a generic "PBF decoding
+  error".
 * Add `--drop-by-attribute-as-needed=`*attribute* to drop the features with
   the lowest values of a numeric attribute from oversized tiles, and
   `--drop-by-attribute-order=desc` to drop the highest values instead.