Accept the per-strategy color property in policies

[jzonthemtn]

Implements the engine side of philterd/phisql#31 for the Python port: accept the optional per-strategy color property added to the redaction-policy schema.

Blocked by philterd/phisql#31. Do not start until that RFC is accepted and the change lands in redaction-policy schema 1.2.0 (an additive edit in place of the current schema version).

Scope

phileas-python is a text redaction engine. It has no PDF or image rendering path today (no PDF redactor, no graphical bounding boxes), so color has no rendering effect here. The requirement is compatibility: a policy that sets color on a strategy must load and redact text exactly as it does today, with color accepted and ignored. This keeps a single policy portable across the PDF-capable engine (phileas, Java) and the text engine.

Acceptance criteria

• The strategy model (phileas/policy/strategy.py) accepts an optional color field without error.
• A policy with color set on one or more strategies loads and redacts text identically to the same policy without color (no behavior change, and no warning that implies malfunction).
• Validation against redaction-policy schema 1.2.0 (the revision that adds color, wherever the project pins or validates the schema) passes for colored policies.
• A test round-trips a colored-strategy policy and asserts the text output is unchanged.
• Documentation is updated if the project documents strategy properties.

Note for a future PDF path

If a PDF or image redaction path is ever added to phileas-python, it must honor color per philterd/phisql#31: named set black, white, red, orange, yellow, green, blue, gray, or 6-digit #RRGGBB, falling back to black for anything else, with per-span color resolving to the redacting strategy's color, then config.pdf.redactionColor, then black. Recorded here for reference; not required by this issue.

[jzonthemtn]

The PhiSQL side is merged (philterd/phisql#32, closing RFC philterd/phisql#31): color is now an optional property on baseFilterStrategy and dateFilterStrategy in redaction-policy schema 1.2.0 (edited in place). This unblocks the engine work here.

For reference, the merged contract:

• Per span, the bar color resolves to the redacting strategy's color, then config.pdf.redactionColor, then black.
• Accepts a named color (black, white, red, orange, yellow, green, blue, gray) or a 6-digit #RRGGBB hex; an unrecognized or malformed value renders black.
• No effect on text redaction.