feat(m2): Projector Linear(256→896)+LayerNorm (T2.2)

- src/tsmm/model/projector.py: Projector (Linear + LayerNorm).
- tests/test_projector.py: 5 tests (shape, Qwen hidden alignment,
  LayerNorm present, gradient flow, no-NaN).
- 66 tests passing.

src/tsmm/model/projector.py

@@ -0,0 +1,22 @@
+"""Projector (T2.2): maps TS tokens from encoder dim to LLM hidden dim.
+
+``Linear(d → h)`` + ``LayerNorm``. Output feeds as soft tokens into the LLM
+``inputs_embeds`` (see ``model/multimodal.py``, T2.3).
+
+Design ref: §2.2 — Projector = Linear(256→896) + LayerNorm.
+"""
+from __future__ import annotations
+
+import torch
+from torch import nn
+
+
+class Projector(nn.Module):
+    def __init__(self, in_dim: int = 256, out_dim: int = 896) -> None:
+        super().__init__()
+        self.linear = nn.Linear(in_dim, out_dim)
+        self.norm = nn.LayerNorm(out_dim)
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        # x: [..., in_dim] → [..., out_dim]
+        return self.norm(self.linear(x))