chore: fix golangci-lint findings (dead code, ineffassign, staticcheck)

[euxaristia]

Summary

Small cleanup pass from running golangci-lint locally (installed it after CodeRabbit's truncateHeadTail nitpick on #476 turned out to have no equivalent check in this repo's actual CI, which only runs go vet).

Changes

• Remove three unused functions found by the unused linter: safeRequestedPrefix, safeShellCommandTokens (internal/agent/command_prefix.go), and truncateHeadTail (internal/tools/bash.go). Each was a thin wrapper with no remaining callers.
• Drop an ineffectual assignment in stringListArgWebSearch (internal/tools/web_search.go): every return path after it already sets the named return explicitly, so the assignment never took effect.
• Simplify a negated-and condition in partition_cache_stable_test.go via De Morgan's law.
• Use strings.Contains instead of strings.Index(...) < 0 in edit_replacers.go.
• Fix error string style (staticcheck ST1005): lowercase "unsafe redirect URL" and drop the trailing period from webFetchPublicOnlyHint in web_fetch.go, updating the one test that asserted on the old casing.

Deliberately left the errcheck findings (unchecked defer file.Close() / response.Body.Close() / Write() errors) alone. Those are stylistic, not correctness bugs, and this repo's CI doesn't run golangci-lint at all, so there's no actual gate to satisfy there.

Test plan

• go build ./...
• go vet ./... (clean, matches actual CI)
• go test ./internal/agent/... ./internal/tools/... (pass)
• golangci-lint run ./internal/agent/... ./internal/tools/... --enable-only unused,ineffassign,staticcheck (0 issues, down from 6)

Summary by CodeRabbit

• Bug Fixes

  • Improved the wording and consistency of a few error messages shown during unsafe redirect handling and web fetch prompts.
  • Tightened validation and matching behavior in some command and edit workflows for more reliable results.

• Refactor

  • Simplified several internal code paths and cleanup logic without changing expected user-facing behavior.
  • Updated test assertions to better reflect the current output format.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: a7753e38-d345-471c-aa32-e799c5a9b48e

📥 Commits

Reviewing files that changed from the base of the PR and between 95ccd5b and 14f60dc.

📒 Files selected for processing (7)

• internal/agent/command_prefix.go
• internal/agent/partition_cache_stable_test.go
• internal/tools/bash.go
• internal/tools/edit_replacers.go
• internal/tools/web_fetch.go
• internal/tools/web_fetch_test.go
• internal/tools/web_search.go

💤 Files with no reviewable changes (3)

• internal/tools/web_search.go
• internal/agent/command_prefix.go
• internal/tools/bash.go

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Walkthrough

This PR removes unused helper functions (safeRequestedPrefix, safeShellCommandTokens, truncateHeadTail), simplifies a test conditional and a fuzzy-match check, adjusts message casing/punctuation in web_fetch.go with corresponding test updates, and removes a redundant assignment in web_search.go.

Changes

Cleanup and minor fixes

Layer / File(s)	Summary
Remove unused command-prefix helpers internal/agent/command_prefix.go	Deletes the unused safeRequestedPrefix and safeShellCommandTokens internal helper functions.
Simplify cache ordering test assertion internal/agent/partition_cache_stable_test.go	Rewrites a negated compound condition into direct >= comparisons for verifying tool ordering.
Remove unused truncateHeadTail helper internal/tools/bash.go	Deletes truncateHeadTail, leaving truncateHeadTailWithTotal as the sole truncation implementation.
Simplify fuzzy edit candidate check internal/tools/edit_replacers.go	Replaces strings.Index(...) < 0 with !strings.Contains(...) for equivalent candidate validation.
Adjust web fetch message casing/punctuation internal/tools/web_fetch.go, internal/tools/web_fetch_test.go	Removes trailing period from a hint string and lowercases "unsafe redirect URL" in the error message, updating the test assertion accordingly.
Simplify provided flag handling internal/tools/web_search.go	Removes a redundant standalone provided = true assignment, relying on later explicit returns.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Possibly related PRs

• Gitlawb/zero#218: Both PRs modify the domains argument parsing/validation logic in stringListArgWebSearch.
• Gitlawb/zero#322: Related to the same command-prefix helper removal tied to a segment-based prefix refactor.
• Gitlawb/zero#506: Both PRs touch fuzzyEditMatch's candidate validation logic in edit_replacers.go.

Suggested reviewers: gnanam1990, anandh8x, Vasanthdev2004

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the cleanup pass fixing golangci-lint findings across dead code, ineffassign, and staticcheck issues.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[jatmn]

@Vasanthdev2004

Findings

• [P2] Tie this cleanup to an approved parent issue or maintainer-approved scope
  CONTRIBUTING.md:45
  This PR is from a CONTRIBUTOR account and does not link an approved parent issue, but the project contribution policy says all community PRs require an approved parent issue with the issue-approved label before implementation starts. The change is also a cleanup/refactor pass driven by local golangci-lint output rather than a linked approved bug or feature, which falls under the same scope rule. Please link the approved issue for this cleanup, or get explicit maintainer approval for taking this contributor cleanup outside the issue-first flow.

[kevincodex1]

LGTM