chore(legacy): raise PHPStan to level 9

[pjcdawkins]

Raises the legacy PHP CLI's PHPStan analysis level from 8 to 9 and regenerates the baseline.

What changed

• legacy/phpstan.neon: level: 8 → level: 9
• legacy/phpstan-baseline.neon: regenerated (1403 errors baselined)

Findings

Level 9 enforces strict handling of the mixed type. It produced 1201 new errors across 203 files:

• 1191 are mixed-related — casting mixed to string, accessing offsets on mixed, and passing mixed to typed parameters. These come from untyped API responses and YAML config arrays whose shape PHPStan cannot infer.
• 10 are array-shape return-type mismatches (should return array<string, X> but returns array<string, array>).

All are baselined.

Bug scan

I ran a targeted scan over the only categories that can actually fault at runtime — foreach over a non-iterable mixed (20 sites) and property access on mixed (3 sites) — reading the source at each location. No real bugs were found. In every case the value is guaranteed iterable by one of:

• a Symfony input flag (VALUE_IS_ARRAY / InputArgument::IS_ARRAY),
• an empty() / isset() guard,
• a json_decode null check,
• the CLI's own embedded config (developer-controlled, not user input),
• or the fixed shape of the RELATIONSHIPS environment variable.

The remaining mixed errors are annotation noise, not runtime faults, so no fixes or integration tests were needed.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR raises the legacy PHP CLI’s PHPStan strictness from level 8 to level 9 and updates the PHPStan baseline accordingly, keeping the current legacy codebase passing static analysis at the new level.

Changes:

• Bump PHPStan level from 8 to 9 for the legacy PHP CLI.
• Regenerate phpstan-baseline.neon to reflect the new level 9 findings.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
legacy/phpstan.neon	Raises PHPStan analysis level to 9 and continues to include the baseline.
legacy/phpstan-baseline.neon	Regenerated baseline to ignore newly reported level 9 issues.

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[pjcdawkins]

Heads-up while reviewing the baselined level-9 errors: one of them is a real runtime bug, not annotation noise.

The regenerated baseline includes:

message: "Parameter #1 $argument of static method ...OsUtil::escapeShellArg() expects string, mixed given."
count: 1
path: src/Command/Variable/VariableGetCommand.php

That corresponds to variable:get passing the optional name argument (which is null in the interactive-selection path) to OsUtil::escapeShellArg(), which requires a string. It throws a fatal TypeError after the variable has already been displayed. Fixed in #126 by using $variable->name instead.

It sits in the mixed-passed-to-typed-parameter category, which the bug scan in this PR's description didn't cover (that scan looked at foreach-over-mixed and property-access-on-mixed), so it's not contradicted — but it's a concrete example that this category can fault at runtime, so it may be worth a second look before baselining the rest wholesale.

Once #126 merges, this baseline entry (count 1 for VariableGetCommand.php) becomes obsolete and should be dropped on rebase, or PHPStan will report an unmatched ignore.