CLI - preserve leading .. in --out-dir paths (#4431)

## Problem

`spacetime generate --out-dir ../frontend-ts-src/module-bindings` was
resolving the path incorrectly, stripping the leading `..` component.
Reported in #4429 via a [user report on
Discord](https://discord.com/channels/1037340874172014652/1475935288919462072/1475935288919462072).

## Root Cause

`normalize_path_lexical()` in `spacetime_config.rs` used
`PathBuf::pop()` to handle `..` components, but `pop()` is a no-op on an
empty `PathBuf`. This silently dropped leading `..` segments:

- Input: `../frontend-ts-src/module-bindings`
- Output: `frontend-ts-src/module-bindings` (wrong — `..` was eaten)

## Fix

Replace the `PathBuf`-based normalization with a `Vec<Component>` stack
approach. `..` only cancels a preceding `Normal` component; otherwise it
is preserved. This correctly handles:

- `../foo` → `../foo` (leading `..` preserved)
- `../../a/b` → `../../a/b` (multiple leading `..` preserved)
- `a/b/../c` → `a/c` (inner `..` still resolves)
- `/home/user/project/../foo` → `/home/user/foo` (absolute paths work)

## Testing

Added `test_normalize_path_preserves_leading_dotdot` covering all edge
cases.

Closes #4429

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Co-authored-by: clockwork-labs-bot <bot@clockworklabs.com>
Co-authored-by: clockwork-labs-bot <clockwork-labs-bot@users.noreply.github.com>

Author: clockwork-labs-bot