fix: percent-decode route params extracted from the pathname

[uhyo]

Closes #206

Problem

Navigating to /users/Jo%C3%A3o with path: "/users/:name" yielded params.name === "Jo%C3%A3o" instead of "João". URLPattern.exec() matches against the percent-encoded pathname (location.pathname is always in encoded form) and returns group values as-is, so any param containing spaces, unicode, or reserved characters reached loaders, actions, and components percent-encoded.

Fix

• extractParams in packages/router/src/core/matchRoutes.ts now decodes each group value with decodeURIComponent, falling back to the raw value for malformed sequences (e.g. a lone %) rather than failing the match. All matching paths (exact, fast prefix, and backtracking) funnel through extractParams, so merged parent params are covered too.
• consumedPathname intentionally stays encoded — it is used to slice the remaining pathname for child matching.
• Since the input pathname is guaranteed to be in encoded form, decoding here cannot double-decode.

Tests & docs

• Added tests for unicode decoding, spaces/reserved characters, params inherited from parent routes, and the malformed-sequence fallback.
• Documented the decoding behavior in the Route Parameters section of the Getting Started docs page.

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