Fix: surface a mid-indexing tsserver crash instead of returning {}

[AmirF194]

Root cause

_wait_for_indexing_start_or_completion (and its underlying wait_for_indexing) infer
project-indexing completion purely from $/progress token bookkeeping: when the active
token set drains, _indexing_complete is set and the wait returns True. When tsserver
aborts (e.g. a V8 heap OOM mid cross-file query), typescript-language-server sends a
$/progress "end" for the in-flight token as part of tearing its connection down, which
is structurally identical to a normal completion. _wait_for_cross_file_references_if_needed
then logs "TypeScript cross-file indexing complete" and find_referencing_symbols returns
{} with isError: false, indistinguishable from a symbol that genuinely has no references.

The crash is already observed independently, via window/logMessage (type: 1/Error,
"[tsserver] Exited. Code: null. Signal: SIGABRT"), but the handler only logged it.

Fix

Wire that already-received signal into a _crash_message flag (set from
window_log_message via a small _tsserver_exit_message classifier), and raise a new
TypeScriptServerCrashedError from every path that would otherwise report indexing as
complete: wait_for_indexing, and both early-return branches of
_wait_for_indexing_start_or_completion (not just its tail call into wait_for_indexing,
since a crash observed within the same poll interval as its own $/progress begin/end can
take either early-return branch). This covers the Vue and Svelte companion TypeScript
servers too, since both hold a TypeScriptLanguageServer instance and inherit
window_log_message via _start_server.

Verification

• test/solidlsp/test_typescript_timeout_policy.py::TestTsserverCrashDetection (new): drives
  the reporter's exact $/progress begin -> crash window/logMessage -> $/progress end
  sequence and pins that wait_for_indexing, both branches of
  _wait_for_indexing_start_or_completion, and _wait_for_cross_file_references_if_needed
  all now raise TypeScriptServerCrashedError instead of returning True/{}; also pins
  that an ordinary completion (no crash message) is unaffected.
• Full test_typescript_timeout_policy.py suite (29 tests, all pre-existing + new): passes
  in a clean python:3.11-slim container.
• ruff format --check, ruff check, ty check (pinned ruff==0.12.5, matching CI): clean
  on both changed files.
• Not verified: the actual window/logMessage handler registered inside _start_server
  against a real tsserver crash, since that requires a live language-server process. The
  classification logic it delegates to (_tsserver_exit_message) is unit-tested directly.

Fixes #1814