add solution drafts, add component decomposition , add spec for other docs

docs/02_components/08_State_Estimator/spec.md

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+# State Estimator Component
+
+## Detailed Description
+The **State Estimator** is the "Brain" of the system. It utilizes a **Factor Graph (GTSAM)** to fuse information from all sources:
+- **Relative factors** from L1 (Frame $t-1 \to t$).
+- **Absolute pose factors** from L3 (Frame $t \to$ World).
+- **Prior factors** (Altitude, Smoothness).
+- **User Inputs** (Manual geometric constraints).
+
+It handles the optimization window (Smoothing and Mapping) and outputs the final trajectory. It also manages the logic for "350m outlier" rejection using robust error kernels (Huber/Cauchy).
+
+## API Methods
+
+### `add_frame_update`
+- **Input:** `timestamp: float`, `l1_data: L1Result`, `l3_data: L3Result | None`, `altitude_prior: float`
+- **Output:** `EstimatedState`
+- **Description:**
+    1. Adds a new node to the graph for time $t$.
+    2. Adds factor for L1 (if tracking valid).
+    3. Adds factor for L3 (if global match found).
+    4. Adds altitude prior.
+    5. Performs incremental optimization (iSAM2).
+    6. Returns optimized state `{ lat, lon, alt, roll, pitch, yaw, uncertainty_covariance }`.
+- **Test Cases:**
+    - Sequence with drift -> L3 update snaps trajectory back to truth.
+    - Outlier L3 input (350m off) -> Robust kernel ignores it, trajectory stays smooth.
+
+### `add_user_correction`
+- **Input:** `timestamp: float`, `uav_pixel: tuple`, `sat_coord: LatLon`
+- **Output:** `void`
+- **Description:** Adds a strong "Pin" constraint to the graph at the specified past timestamp and re-optimizes.
+- **Test Cases:**
+    - Retroactive fix -> Updates current position estimate based on past correction.
+
+### `get_current_state`
+- **Input:** `void`
+- **Output:** `EstimatedState`
+- **Description:** Returns the latest optimized pose.
+
+## Integration Tests
+- **Full Graph Test:** Feed synthetic noisy data. Verify that the output error is lower than the input noise (fusion gain).
+
+## Non-functional Tests
+- **Stability:** Ensure graph doesn't explode (numerical instability) over long sequences (2000+ frames).
+