Add AX setup: contexts, ADRs, and grill-with-docs skill

[brickbots]

Summary

Establishes a bounded-context vocabulary for the Catalog, Positioning, and SQM subsystems so future work shares the same language. Produced via a grill-with-docs session over the existing docs/ax/*.md draft glossaries.

• CONTEXT-MAP.md indexes the three contexts and how they relate.
• docs/ax/<area>/CONTEXT.md — canonical glossary per area, with flagged ambiguities and an example dialogue. Companion architecture deep-dives live as docs/ax/<area>.md.
• docs/adr/0001-positioning-vocabulary.md — locks in the pointing.<axis>.<state>.<RA|Dec|Roll> shape, the choice of aligned over scope, and target_pixel as the (Y, X) image-space coordinate. The code rename will land against the proposal dataclasses in python/PiFinder/types/positioning.py.
• docs/adr/0002-sqm-published-value-uncorrected.md — captures the intentional choice to publish raw sqm_final rather than the idealised altitude-corrected number.
• .claude/skills/grill-with-docs/ — the skill that produced the contexts, included so the session can be re-run as the vocabulary evolves.
• CLAUDE.md — points future agents at the new reference docs.

Key vocabulary decisions baked in:

• Catalog: enabled (catalog) vs selected (object), sky object vs catalog listing vs CompositeObject, populated vs fully loaded, logged (technical) vs observed (user-facing).
• Positioning: 2 × 2 matrix pointing.{camera,aligned}.{solve,estimate}; bare "pointing" = pointing.aligned.estimate.
• SQM: dark sequence (multi-frame wizard concept) vs zero-second sample (single-frame runtime), bias_offset ⊆ pedestal, "noise floor" reserved for the published value.

Prototype dataclasses

• Includes proposed dataclasses to be used for an upcoming refactor as it's the file is referenced in the context. These dataclasses are subject to change in a future refactoring PR

Test plan

• Skim CONTEXT-MAP.md and confirm relationships are accurate
• Walk each docs/ax/<area>/CONTEXT.md and confirm terms match how you'd describe them to a new contributor
• Confirm both ADRs reflect intentional choices, not accidents
• Verify python/PiFinder/types/positioning.py is the proposal-dataclass file you intended to ship in this PR (it can be split out if not)
• Check the CLAUDE.md Reference Documentation section is wired to land before Architecture Overview
• Sanity-check that no unrelated files (gerbers, kicad backups) snuck in

🤖 Generated with Claude Code