
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Given an ellipse $C$: $\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1$ ($a > b > 0$) with one vertex at $A(2,0)$ and an eccentricity of $\frac{\sqrt{2}}{2}$. The line $y = x - 1$ intersects the ellipse $C$ at two distinct points $M$ and $N$.  
(1) Find the standard equation of the ellipse $C$;  
(2) Calculate the length of the segment $MN$.

Present the answer in LaTex format: \boxed{Your answer}
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