Add option to count stackable plants as a single plant

[tastybento]

Fixes #53.

Adds the config option Poslovitch suggested on the ticket:

# Count stackable plants (SUGAR_CANE, BAMBOO) as a single plant no matter how tall
# they grow. When false (default), every segment of the plant counts toward the limit.
stacked-plants-count-as-one: false

How it works

One rule, applied in three places: a stackable segment sitting on the same plant is invisible to counting — only the base segment represents the plant.

• process() (all place/grow/spread paths funnel through it): segments above the same plant are skipped for counting, limit checks, and decrements.
• handleBreak(): the existing stem-cascade decrement is disabled when the option is on, since stems were never counted. Breaking a middle stem leaves the plant counted (the base still stands); breaking the base decrements the one counted plant.
• RecountCalculator: the column scan skips a stackable whose block below normalised to the same plant, so recounts agree with live counts.

BAMBOO_SAPLING normalises to BAMBOO (existing variant map), so a stem above a sapling reads as the same plant. Default off preserves today's per-segment behaviour exactly — the config comment tells admins to run a recount after flipping the option.

Tests

Segment-not-counted, base-counted, and break-decrements-exactly-one cases, plus config parsing; the pre-existing cascade test pins the default-off behaviour. Full suite green.

In-game test plan

1. Enable the option, set SUGAR_CANE: 5, restart.
2. Plant 5 canes → 6th blocked. Let them grow to full height → /is limits still 5/5.
3. Break a middle segment of one cane → still 5/5 (plant remains). Break a base → 4/5.
4. /is limits recount at any point → number unchanged.
5. Repeat 2–4 with bamboo (including placing bamboo items on existing stalks — should not change the count).

🤖 Generated with Claude Code

https://claude.ai/code/session_015dbJyrv2uxHfTmiWkqGUJB

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
58.6% Coverage on New Code
0.0% Duplication on New Code

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