Place grounded filter capacitors beside their matching chip pins

[mohan-bee]

Motivation

Grounded filter capacitors connected through nets were packed as generic power/ground rows. In the RP2040 power-supply reproduction, this left C1 far from U2 pin 3 and allowed D2/R1 to determine the layout, while the C4/C18 decoupling row was not anchored to U2.

Reproduction: #181

Change

• recognize grounded signal-filter capacitors as pin-local capacitor groups
• allow a single net-only capacitor to form a dedicated partition without changing directly wired singleton behavior
• anchor net-only capacitor rows to the matching non-ground pins on the selected chip side, then reject placements that collide
• keep power-rail preference for ordinary decoupling capacitors

Evidence

C1 now sits immediately to U2’s left, while C4/C18 form a row immediately to U2’s 3.3 V side. D2 and R1 remain outside those pin-local rows. Existing ADXL345 and power-section snapshots were refreshed for the intentional placement change.

Tests

• added grounded signal-filter identification coverage
• added numeric singleton placement assertions for chip gap, pin alignment, and overlap rejection
• bun test — 72 passed, 1 skipped
• bun run build

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Project	Deployment	Actions	Updated (UTC)
matchpack	Ready	Preview, Comment	Jul 29, 2026 11:36am