remove the get_host_journal MCP tool and its capability

swarm-logs covers every host-tier unit this tool could reach, so the
second, capability-gated path into host journald earns nothing and is
removed outright rather than disabled behind a flag.

Removed end to end: the MCP tool definition + handler, the
GetHostJournal/HostJournal wire variants, hive-c0re's
dispatch_host_journal handler, the ReadHostJournal capability, and the
harness-side capability->--allowedTools gate. get_host_journal was the
only capability that mapped to an MCP tool, so allowed_capability_tools
could only ever return an empty vec; it goes too rather than linger as a
function that provably does nothing.

capabilities::has_cap/caps_for stay: #4624 gave ManageRootAgent's
bind-mount enforcement (hive-c0re/src/lifecycle/host_config.rs) a
second caller of has_cap, so they're no longer callerless once this
lands on top of it.

hive-sh4re's journal module (JournalPriority) had no consumer outside
this tool and is deleted.

An existing capabilities.json still naming read_host_journal does not
error: capabilities::prune_unknown drops unrecognised names with a
warn!, and an agent left with no capabilities has its entry removed. No
migration step is needed.

Untouched: hive-c0re/src/dashboard/journal.rs's
read_host_journal_response, which matches the name but is the private
helper behind the operator-only GET /api/journal-host dashboard route
and carries no capability check.

hive-agent/src/mcp_config.rs

@@ -30,37 +30,6 @@ pub const DEFAULT_MCP_HTTP_PORT: u16 = 8790;
 /// drift.
 pub use hive_sh4re::permissions::{builtin_tools_arg, effective_tool_groups};
 
-/// `HIVE_CAPABILITIES` env var injected by `meta::render_flake` when the
-/// operator grants capabilities to this agent. Comma-separated
-/// `hive_sh4re::permissions::Capability` `snake_case` names. Absent = no extra capabilities.
-const CAPABILITIES_ENV: &str = "HIVE_CAPABILITIES";
-
-/// Returns the MCP tool names (without `mcp__hyperhive__` prefix) that are
-/// unlocked by the agent's current capability set. These are added to the
-/// `--allowedTools` list so claude can call them without prompting, and
-/// hive-c0re performs a second server-side capability check before executing.
-fn allowed_capability_tools() -> Vec<String> {
-    let raw = match std::env::var(CAPABILITIES_ENV) {
-        Ok(v) if !v.trim().is_empty() => v,
-        _ => return vec![],
-    };
-    let mut tools = Vec::new();
-    for token in raw.split(',') {
-        let t = token.trim().to_ascii_lowercase();
-        match t.as_str() {
-            "read_host_journal" => tools.push("get_host_journal".to_owned()),
-            // manage_root_agent exposes no MCP tool at all: it is a
-            // host-side grant, enforced by hive-c0re when it computes the
-            // container's bind mounts. Nothing for the harness to register.
-            "manage_root_agent" => {}
-            unknown => {
-                tracing::warn!(capability = %unknown, "unrecognised capability in HIVE_CAPABILITIES — skipped");
-            }
-        }
-    }
-    tools
-}
-
 /// Tool group an extra (out-of-process) MCP server is gated behind, if any.
 ///
 /// Most `services.hyperhive.agent.extraMcpServers` entries are ungated — available whenever
@@ -161,13 +130,6 @@ pub fn allowed_tools_arg() -> String {
         .map(ToOwned::to_owned)
         .collect();
     all.extend(allowed_mcp_tools(&groups));
-    // Capability-gated MCP tools: added to --allowedTools when HIVE_CAPABILITIES
-    // includes the corresponding capability. hive-c0re performs a second
-    // server-side check, so this is a usability gate (no annoying prompts),
-    // not the security boundary.
-    for tool in allowed_capability_tools() {
-        all.push(format!("mcp__{SERVER_NAME}__{tool}"));
-    }
     all.join(",")
 }
 

hive-agent/src/stream_enrich.rs

@@ -501,7 +501,6 @@ fn tool_icon(name: &str) -> &'static str {
         "mcp__matrix__list_rooms"
         | "mcp__matrix__list_room_members"
         | "mcp__matrix__list_invites" => "📋",
-        "mcp__hyperhive__get_host_journal" => "📜",
         "mcp__matrix__read_room" | "Read" => "📖",
         "mcp__matrix__mark_read" => "👁️",
         "mcp__bash__kill" => "🛑",
@@ -645,25 +644,6 @@ fn fmt_hyperhive_tool(name: &str, short: &str, input: &Value) -> String {
                 .map_or_else(|| "?".to_owned(), |n| n.to_string());
             format!("{short} ≤{up_to}")
         }
-        "mcp__hyperhive__get_host_journal" => {
-            let mut parts = Vec::new();
-            if let Some(c) = input.get("container").and_then(Value::as_str) {
-                parts.push(c.to_owned());
-            } else if let Some(u) = input.get("unit").and_then(Value::as_str) {
-                parts.push(u.to_owned());
-            }
-            if let Some(g) = input.get("grep").and_then(Value::as_str) {
-                parts.push(format!("/{g}/"));
-            }
-            if let Some(l) = input.get("lines").and_then(Value::as_u64) {
-                parts.push(format!("{l}L"));
-            }
-            if parts.is_empty() {
-                format!("{short}()")
-            } else {
-                format!("{short} {}", parts.join(" · "))
-            }
-        }
         "mcp__hyperhive__remind" => fmt_hyperhive_remind(short, input),
         "mcp__hyperhive__list_schedules"
         | "mcp__hyperhive__cancel_schedule"