Set 69-column lint policy in `ruff.toml`

Enable `E501` at the shared 69-column source limit so `ruff`
surfaces the repository's existing line-length debt.

Keep the debt visible rather than rewriting legacy source, and
record the incremental checker plan for making changed-line
enforcement landable.

Prompt-IO: ai/prompt-io/opencode/20260825T181102Z_3690e43a_prompt_io.md

(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))

ai/prompt-io/opencode/20260825T181102Z_3690e43a_prompt_io.md

@@ -0,0 +1,36 @@
+---
+model: openai/gpt-5.6-sol
+service: opencode
+session: ses_fd403c9c9ffe625w99Tr0ALQBN
+timestamp: 2026-08-25T18:11:02Z
+git_ref: 3690e43a
+scope: config
+substantive: true
+raw_file: 20260825T181102Z_3690e43a_prompt_io.raw.md
+---
+
+## Prompt
+
+Enforce the 69-column Python source limit through Ruff and record a
+follow-up for richer project-specific style checks.
+
+## Response summary
+
+Enabled E501 at 69 columns and documented a later changed-line
+token/AST checker for style rules Ruff cannot represent. Isolated the
+configuration on a dedicated follow-up branch after measuring the
+existing repository lint debt.
+
+## Files changed
+
+- `ruff.toml` - enables 69-column E501 enforcement and records
+  follow-up lint work.
+
+## Human edits
+
+The human initially selected immediate global enforcement and
+explicitly requested the richer-checker TODO. After review exposed
+1,548 existing diagnostics, the human directed the work onto an
+independent linting branch and deferred landing until incremental
+enforcement is implemented. The agent applied the config and transfer;
+no direct manual source edits were identified.

ai/prompt-io/opencode/20260825T181102Z_3690e43a_prompt_io.raw.md

@@ -0,0 +1,24 @@
+---
+model: openai/gpt-5.6-sol
+service: opencode
+timestamp: 2026-08-25T18:11:02Z
+git_ref: main
+diff_cmd: git diff HEAD~1..HEAD -- ruff.toml
+---
+
+## Prompt
+
+Enable Ruff enforcement of the shared 69-column Python source limit in
+Modden, Piker, and Tractor. Add a TODO for a later changed-line token/AST
+checker covering project rules Ruff cannot express.
+
+## Response
+
+Configured Ruff's formatter/lint line length to 69 and enabled E501. Added a
+follow-up TODO for boolean layout, local annotation placement, docstring
+quoting and rationale, and symbol-qualified technical prose.
+
+> `git diff HEAD~1..HEAD -- ruff.toml`
+
+The configuration parses successfully. Existing Tractor package/test debt is
+1,469 E501 diagnostics; it was reported rather than reformatted implicitly.

plans/opencode/py_codestyle_linting.md

@@ -0,0 +1,97 @@
+# Incremental Python Style Enforcement
+
+## Objective
+
+Enforce the mechanically checkable parts of `/py-codestyle` on new and
+changed Python lines without requiring an immediate repository-wide
+cleanup. Keep subjective prose guidance in review policy and expose
+legacy debt separately from blocking CI.
+
+## Current State
+
+- `ruff.toml` sets the intended 69-column limit and enables `E501`.
+- A package-and-test scan reports 1,548 existing violations.
+- Ruff can enforce line length, ordinary syntax rules, unused f-string
+  prefixes, and configured quote style.
+- Ruff cannot directly encode several project-specific layout,
+  docstring, annotation, and technical-prose policies.
+
+The initial configuration is branch scaffolding, not a landable final
+state. The implementation must make changed-code enforcement usable
+before this branch targets `main`.
+
+## Policy Matrix
+
+Document each `/py-codestyle` rule under one enforcement class:
+
+1. Ruff lint rule, enabled directly when the repository is clean.
+2. Ruff formatter setting, used for intentionally formatted files.
+3. Deterministic token or AST check, enforced on changed lines.
+4. Review-only guidance where automation would produce false positives.
+
+Start with native checks for `E501`, `F541`, quote style, import and
+syntax errors. Use custom checks for exact docstring delimiters and
+shape, multiline string construction, double-newline source layout,
+f-string continuation consistency, local annotation placement, and
+boolean-expression layout. Keep symbol-qualified technical prose and
+regression-test rationale as review guidance unless a low-noise warning
+can be demonstrated.
+
+## Changed-Line Harness
+
+Add `scripts/check_py_codestyle.py` with these responsibilities:
+
+- Read a base revision and collect added line ranges from `git diff
+  --unified=0`.
+- Treat every line in an added Python file as changed.
+- Run Ruff with JSON output and the incremental native-rule set.
+- Report only diagnostics intersecting added line ranges.
+- Run token/AST checks and apply the same changed-line filter.
+- Return a nonzero status only for changed-code violations.
+- Offer a separate nonblocking full-tree debt-report mode.
+
+Keep `E501` out of the default global Ruff selection until the legacy
+count reaches zero. The harness should request it explicitly so normal
+repository lint remains useful during migration.
+
+## Verification
+
+Add focused checker tests covering:
+
+- diff range parsing, deleted lines, renames, and new files;
+- 69-column boundaries with indentation and string syntax;
+- compliant and noncompliant docstring delimiters and closing shape;
+- f-string continuation and double-newline source layout;
+- boolean layout and local annotation placement;
+- diagnostics on untouched legacy lines being ignored;
+- diagnostics on newly touched legacy lines becoming blocking.
+
+Run the checker against a fixture base and against the branch diff. Run
+the existing Ruff checks without incremental rules to prove the normal
+lint path remains usable.
+
+## CI Integration
+
+Add a dedicated CI step that derives the pull-request base commit from
+the event payload and invokes the changed-line harness. Preserve a local
+`--base main` mode for developers. Emit normal file, line, column, and
+rule identifiers so forge annotations remain navigable.
+
+Publish the full-tree debt count as nonblocking output. Do not hide or
+silently rewrite existing source violations.
+
+## Commit Boundaries
+
+1. Record the 69-column policy scaffold and provenance.
+2. Add the changed-line Ruff harness and its tests.
+3. Add deterministic token/AST policy checks and fixtures.
+4. Wire the harness into CI and document local usage.
+5. Enable native rules globally only after their legacy counts reach
+   zero, using separate cleanup commits where needed.
+
+## Deferred
+
+Type-checking migration belongs in a separate branch. It should use the
+same incremental principle: establish the tool configuration and debt
+inventory, gate new or changed code, publish nonblocking full-tree debt,
+and tighten global enforcement as annotations and defects are repaired.

ruff.toml

@@ -31,8 +31,8 @@ exclude = [
     "venv",
 ]
 
-# Same as Black.
-line-length = 88
+# Project source style limit.
+line-length = 69
 indent-width = 4
 
 # assume latest minor cpython
@@ -42,11 +42,15 @@ target-version = "py313"
 # Enable Pyflakes (`F`) and a subset of the pycodestyle (`E`)  codes by default.
 # Unlike Flake8, Ruff doesn't enable pycodestyle warnings (`W`) or
 # McCabe complexity (`C901`) by default.
-select = ["E4", "E7", "E9", "F"]
+select = ["E4", "E7", "E9", "E501", "F"]
 ignore = [
   'E402',  # https://docs.astral.sh/ruff/rules/module-import-not-at-top-of-file/
 ]
 
+# TODO: add a changed-line token/AST checker for py-codestyle rules
+# Ruff cannot express: boolean layout, local annotation placement,
+# docstring quoting/rationale, and symbol-qualified technical prose.
+
 # Allow fix for all enabled rules (when `--fix`) is provided.
 fixable = ["ALL"]
 unfixable = []