Fix #40, #41, #71: make aether:install safe to re-run and truthful about the environment

[corgab]

Summary

Three defects in AetherInstallCommand, fixed together because they live in the same file and the same flow:

• [commands] aether:install force-overwrites config/aether.php with no confirmation #40 publishConfig() ran vendor:publish --force unconditionally, so re-running aether:install silently wiped a hand-edited config/aether.php.
• [commands] aether:install runs a billable test circuit on AETHER_DRIVER=aws, and fails the happy path after creating a venv #41 the smoke test used $manager->circuit() on the configured default driver, so AETHER_DRIVER=aws made the installer submit a real, billable task; and after createVenv() the smoke test still ran through the interpreter configured at boot, so the documented happy path ended in "The test circuit failed to run".
• [commands] aether:install always reports amazon-braket-sdk as NOT INSTALLED because braket has no __version__ #71 checkDependencies() probed braket.__version__, which does not exist (braket is a namespace package), so the SDK was reported NOT INSTALLED on every machine and the success path was unreachable.

Plan

• Keep an existing config, ask before overwriting when interactive, add --force for the deliberate overwrite.
• Pin the smoke test to the local simulator and route it through the interpreter the command just verified or created, reusing the manager's own driver wiring.
• Probe the SDK through importlib.metadata, compare with the floor pinned in bin/python/requirements.txt, and make every hint name the configured interpreter.

Changes

• Signature gains {--force : Overwrite an existing config/aether.php}. publishConfig() publishes when the file is missing or --force is given; otherwise it asks config/aether.php already exists. Overwrite it with the package default? in an interactive terminal and keeps the file in a non-interactive run, reporting KEPT (pass --force to overwrite).
• runTestCircuit(QuantumDevice $device) builds (new CircuitBuilder($device, 'local'))->qubits(1)->h(0)->measure()->run(). verifyInstallation() picks the device: $manager->localDriver($venvPython) when createVenv() just produced an interpreter, otherwise $manager->driver('local'). QuantumManager::localDriver(?string $pythonPath) and bridge(?string $pythonPath) are the single source of that wiring.
• createVenv() and handleMissingDependencies() return the venv interpreter path on full success, null otherwise; the dependency install is skipped when the venv could not be created, and a failure falls back to the manual instructions instead of advertising an interpreter that does not exist.
• checkDependencies() probes importlib.metadata.version("amazon-braket-sdk"), compares with the floor parsed by parseRequirementsFloor() from requirements.txt, and prints <version> (requires >= <floor>) plus <python> -m pip install --upgrade -r ... when too old. requirementsPath() replaces three copies of the relative path.
• showManualInstructions() uses the configured interpreter and venvPythonPath(), so the commands are right on Windows and with a non-default python3.
• A missing interpreter now returns FAILURE instead of printing "Aether installation complete".
• README Installation section lists what the command does; CLAUDE.md gains one conventions bullet. No config change, no new dependencies.

Tests

AetherInstallCommandTest, driven by a fake #!/bin/sh interpreter answering --version and the -c probe (each test removes only the fakes it created):

• config kept without --force (file unchanged), overwritten with --force, published when absent, kept when the interactive confirmation is declined;
• SDK reported with its version when at or above the floor, flagged with requires >= and the floor when older with an upgrade hint naming the interpreter, NOT INSTALLED plus interpreter-specific manual instructions when the probe fails;
• floor parsing from a requirements-shaped string;
• the smoke test resolves driver('local') on the manager and nothing else, with aether.default = aws;
• a smoke test whose run throws returns FAILURE; a missing interpreter returns FAILURE without the completion banner.

Local: pint passed, pest 804 tests passed.

Closes #40
Closes #41
Closes #71