feat(syslog): a source's lines to read and search, on its page, its host's and its SNMP device's, and over MCP (#6000)

- /plugins/syslog/sources/<id>: the lines newest first, loading as you
  scroll, filtered by severity and worse, app, text and time, with day
  dividers and times to the second in the reader's zone.
- The Syslog page links each source and shows its lines in the last hour.
- A Syslog panel on a host's page and an SNMP device's: the newest lines of
  the sources bound to it or at its address.
- MCP: list_syslog_sources and search_syslog (source, host, text, severity
  and worse, app, range, paging by next_before).
- Shared: escape_like moves to steward/core/like.py and cut_middle to the
  MCP shaping module, replacing four inline copies; |when takes seconds=.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

steward/mcp/tools/_shape.py

@@ -25,6 +25,8 @@ from steward.mcp._context import mcp_app
 T = TypeVar("T")
 
 SERIES_POINTS = 60  # max points in any returned series
+# The longest log line a tool returns whole (container logs, syslog).
+LOG_LINE_CHARS = 2000
 
 
 def db_session():
@@ -134,6 +136,14 @@ def pick(want: str, rows: Iterable[T], *, kind: str, list_tool: str,
     raise ValueError(f"no {kind} named or with id {want!r}.{hint} {list_tool} lists them.")
 
 
+def cut_middle(text: str, limit: int = LOG_LINE_CHARS) -> str:
+    """Keep both ends of an over-long line and say how much of the middle went."""
+    if text is None or len(text) <= limit:
+        return text
+    keep = limit // 2
+    return f"{text[:keep]} [… {len(text) - 2 * keep} characters omitted …] {text[-keep:]}"
+
+
 def redact_url(url: str) -> str:
     """Drop a password from a URL's userinfo; the rest stays readable."""
     try: