refactor: collapse single-implementation interfaces

Nine interfaces had exactly one implementation and no test double — they existed
only to be named twice in a DI registration: IFindingsStore, IFindingsStoreLocator,
IPrimeScheduleSignal, IRefineRunner, IWeekReportService, IMergeCoordinator,
IMissionControlPane, IOnlineLoginService, ITaskListFilter. Consumers now depend on
the concrete type; the DTO records that shared those files moved next to their
implementation. IInteractiveLaunchSpecService stays — it carries 54 lines of
contract documentation, which is not ceremony.

IMergeCoordinator in particular had a redundant null object: MergeCoordinator with
a null Handler already no-ops, and every test used the real class with Handler set.

Filtering/ collapses from 8 files to 1. ITaskListFilter and TaskListFilterBase were
a double abstraction over four predicates, with MatchesAsContext => false declared
in both. SmartFlagFilter also compiled its expression twice (its own _flag plus the
inherited Matches cache) — it now uses the cache.

StaticTokenAuthProvider was in src but production uses ZitadelAuthProvider; it is
a test double, so it moves to the test project. Its own test goes away with it.

src/ClaudeDo.Worker/Planning/WindowsTerminalLauncher.cs

@@ -86,7 +86,7 @@ public sealed class WindowsTerminalLauncher : ITerminalLauncher
         return Task.CompletedTask;
     }
 
-    // The raw claude CLI args for a --resume launch, shared with InteractiveLaunchSpecService
+    // The raw claude CLI args for a --resume launch, shared with IInteractiveLaunchSpecService
     // (which needs the bare Exe/Args pair for a ConPTY host, not a wrapped pwsh command line).
     internal static IReadOnlyList<string> BuildResumeArgs(string claudeSessionId) =>
         new[] { "--resume", claudeSessionId };
@@ -99,7 +99,7 @@ public sealed class WindowsTerminalLauncher : ITerminalLauncher
         BuildPwshCommand(claudePath, BuildPlanningStartArgs(ctx));
 
     // The raw claude CLI args for an interactive planning START, shared with the embedded-ConPTY
-    // planning path (InteractiveLaunchSpecService), which needs the bare Exe/Args pair rather than
+    // planning path (IInteractiveLaunchSpecService), which needs the bare Exe/Args pair rather than
     // a pwsh-wrapped command line. Arg order matters: variadic flags (--allowedTools, --add-dir)
     // come first; the single-line kickoff prompt is positional, so it must follow a single-value
     // flag (--append-system-prompt-file) or a variadic flag would swallow it.
@@ -176,7 +176,7 @@ public sealed class WindowsTerminalLauncher : ITerminalLauncher
             ?? throw new TerminalLaunchException("Failed to start Windows Terminal process.");
     }
 
-    // Not private: reused by InteractiveLaunchSpecService to resolve the claude executable
+    // Not private: reused by IInteractiveLaunchSpecService to resolve the claude executable
     // for a ConPTY-hosted launch spec the same way a wt-launched terminal resolves it.
     internal static string? Resolve(string pathOrName)
     {