navi-offroute: drop unused connection cache from HPAManifest (cleanup)

The connection cache field (_conns) and get_connection() method were
shipped in PR #53 "ready for future use" but never consumed by the v1
dispatch path: astar_hpa_multimode opens its own sqlite connection per
call (astar.py:752) and changing that signature was out of scope.

Per self-review of PR #53: shipping dead code in a PR is wrong even
when the rationale is "future PRs will use it." Removing it here keeps
the manifest module focused on lookup; whoever needs the cache later
can add it alongside the use site.

  - Drop _conns field, get_connection() method.
  - Drop sqlite3 + Dict imports (no longer referenced).
  - Drop test_get_connection_caches_per_path.

23 deletions, 2 insertions. No production behaviour change.

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

backend/services/navi_offroute/hpa_manifest.py

@@ -10,9 +10,8 @@ neither env var set -> HPA disabled (same as today).
 import json
 import logging
 import os
-import sqlite3
 from dataclasses import dataclass, field
-from typing import Dict, List, Optional
+from typing import List, Optional
 
 logger = logging.getLogger(__name__)
 
@@ -43,10 +42,8 @@ class TileDBEntry:
 
 @dataclass
 class HPAManifest:
-    """Registry of regional tile DBs + lazy per-path sqlite connection cache.
-    The cache is process-local mutable state; entries are immutable after load."""
+    """Registry of regional tile DBs. Immutable after load."""
     entries: List[TileDBEntry] = field(default_factory=list)
-    _conns: Dict[str, sqlite3.Connection] = field(default_factory=dict)
 
     def enabled(self) -> bool:
         return len(self.entries) > 0
@@ -73,17 +70,6 @@ class HPAManifest:
         return self.dbs_for_chunks(min(cx0, cx1), max(cx0, cx1),
                                    min(cy0, cy1), max(cy0, cy1))
 
-    def get_connection(self, abs_path: str) -> sqlite3.Connection:
-        """Read-only sqlite connection cached for the life of the process. v1
-        dispatch (astar_hpa_multimode) opens its own connection per call and does
-        not yet use this cache; multi-region UNION + admin endpoints will."""
-        conn = self._conns.get(abs_path)
-        if conn is None:
-            conn = sqlite3.connect(f"file:{abs_path}?mode=ro", uri=True)
-            self._conns[abs_path] = conn
-        return conn
-
-
 # ── loaders ──────────────────────────────────────────────────────────────────
 
 def _load_from_dir(dir_path: str) -> HPAManifest:

backend/services/navi_offroute/tests/test_hpa_manifest.py

@@ -106,12 +106,3 @@ def test_load_env_disabled_paths(tmp_path, monkeypatch):
     # neither var set -> empty
     monkeypatch.delenv(hm.ENV_LEGACY, raising=False)
     assert not hm.load().enabled()
-
-
-def test_get_connection_caches_per_path(tmp_path):
-    import sqlite3
-    p = _touch(str(tmp_path), "x.db")
-    with sqlite3.connect(p) as c:
-        c.execute("CREATE TABLE t (x INTEGER)")
-    m = hm.HPAManifest(entries=[hm.TileDBEntry("x", p, None)])
-    assert m.get_connection(p) is m.get_connection(p)