feat: scaffold remove command foundations

specs/003-add-remove-command/research.md

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+# Phase 0 Research: Remove Command with Sequential Multi-Pattern Support
+
+## Decision: Sequential removal executed in-memory before filesystem writes
+- **Rationale**: Computing the full rename plan in memory guarantees deterministic previews,
+  simplifies conflict detection, and avoids partial renames that could increase IO load or leave the
+  filesystem inconsistent.
+- **Alternatives considered**:
+  - *Apply-and-check per token*: rejected due to repeated filesystem mutations and difficulty keeping
+    undo history coherent.
+  - *Streaming rename per file*: rejected because conflicts can only be detected after all tokens
+    apply.
+
+## Decision: Dedicated `internal/remove` package mirroring replace architecture
+- **Rationale**: Keeps responsibilities separated (parser, engine, summary) and allows reuse of
+  traversal/history helpers. Aligns with Composable Rule Engine principle.
+- **Alternatives considered**:
+  - *Extending replace package*: rejected to avoid coupling distinct behaviors and tests.
+  - *Embedding logic directly in command*: rejected for testability and maintainability reasons.
+
+## Decision: Empty-result handling warns and skips rename
+- **Rationale**: Removing multiple tokens could produce empty basenames; skipping prevents creating
+  invalid filenames while still informing the user.
+- **Alternatives considered**:
+  - *Allow empty names*: rejected as unsafe and difficult to undo cleanly on certain filesystems.
+  - *Hard fail entire batch*: rejected because unaffected files should still be processed.
+
+## Decision: Ledger metadata records ordered tokens and counts
+- **Rationale**: Automation and undo workflows need insight into which tokens were removed and how
+  often, mirroring replace’s metadata for consistency.
+- **Alternatives considered**:
+  - *Only store operations*: insufficient for auditing complex removals.
+
+## Decision: CLI help & quickstart emphasize ordering semantics
+- **Rationale**: Sequential behavior is the primary mental model difference from other commands; clear
+  documentation reduces support load and user confusion.
+- **Alternatives considered**:
+  - *Rely on examples alone*: risk of users assuming parallel removal and encountering surprises.